Back to home page

OSCL-LXR
 
 

     

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 #include <crypto/hash.h>
0003 #include <linux/export.h>
0004 #include <linux/bvec.h>
0005 #include <linux/fault-inject-usercopy.h>
0006 #include <linux/uio.h>
0007 #include <linux/pagemap.h>
0008 #include <linux/highmem.h>
0009 #include <linux/slab.h>
0010 #include <linux/vmalloc.h>
0011 #include <linux/splice.h>
0012 #include <linux/compat.h>
0013 #include <net/checksum.h>
0014 #include <linux/scatterlist.h>
0015 #include <linux/instrumented.h>
0016 
0017 #define PIPE_PARANOIA /* for now */
0018 
0019 /* covers ubuf and kbuf alike */
0020 #define iterate_buf(i, n, base, len, off, __p, STEP) {      \
0021     size_t __maybe_unused off = 0;              \
0022     len = n;                        \
0023     base = __p + i->iov_offset;             \
0024     len -= (STEP);                      \
0025     i->iov_offset += len;                   \
0026     n = len;                        \
0027 }
0028 
0029 /* covers iovec and kvec alike */
0030 #define iterate_iovec(i, n, base, len, off, __p, STEP) {    \
0031     size_t off = 0;                     \
0032     size_t skip = i->iov_offset;                \
0033     do {                            \
0034         len = min(n, __p->iov_len - skip);      \
0035         if (likely(len)) {              \
0036             base = __p->iov_base + skip;        \
0037             len -= (STEP);              \
0038             off += len;             \
0039             skip += len;                \
0040             n -= len;               \
0041             if (skip < __p->iov_len)        \
0042                 break;              \
0043         }                       \
0044         __p++;                      \
0045         skip = 0;                   \
0046     } while (n);                        \
0047     i->iov_offset = skip;                   \
0048     n = off;                        \
0049 }
0050 
0051 #define iterate_bvec(i, n, base, len, off, p, STEP) {       \
0052     size_t off = 0;                     \
0053     unsigned skip = i->iov_offset;              \
0054     while (n) {                     \
0055         unsigned offset = p->bv_offset + skip;      \
0056         unsigned left;                  \
0057         void *kaddr = kmap_local_page(p->bv_page +  \
0058                     offset / PAGE_SIZE);    \
0059         base = kaddr + offset % PAGE_SIZE;      \
0060         len = min(min(n, (size_t)(p->bv_len - skip)),   \
0061              (size_t)(PAGE_SIZE - offset % PAGE_SIZE)); \
0062         left = (STEP);                  \
0063         kunmap_local(kaddr);                \
0064         len -= left;                    \
0065         off += len;                 \
0066         skip += len;                    \
0067         if (skip == p->bv_len) {            \
0068             skip = 0;               \
0069             p++;                    \
0070         }                       \
0071         n -= len;                   \
0072         if (left)                   \
0073             break;                  \
0074     }                           \
0075     i->iov_offset = skip;                   \
0076     n = off;                        \
0077 }
0078 
0079 #define iterate_xarray(i, n, base, len, __off, STEP) {      \
0080     __label__ __out;                    \
0081     size_t __off = 0;                   \
0082     struct folio *folio;                    \
0083     loff_t start = i->xarray_start + i->iov_offset;     \
0084     pgoff_t index = start / PAGE_SIZE;          \
0085     XA_STATE(xas, i->xarray, index);            \
0086                                 \
0087     len = PAGE_SIZE - offset_in_page(start);        \
0088     rcu_read_lock();                    \
0089     xas_for_each(&xas, folio, ULONG_MAX) {          \
0090         unsigned left;                  \
0091         size_t offset;                  \
0092         if (xas_retry(&xas, folio))         \
0093             continue;               \
0094         if (WARN_ON(xa_is_value(folio)))        \
0095             break;                  \
0096         if (WARN_ON(folio_test_hugetlb(folio)))     \
0097             break;                  \
0098         offset = offset_in_folio(folio, start + __off); \
0099         while (offset < folio_size(folio)) {        \
0100             base = kmap_local_folio(folio, offset); \
0101             len = min(n, len);          \
0102             left = (STEP);              \
0103             kunmap_local(base);         \
0104             len -= left;                \
0105             __off += len;               \
0106             n -= len;               \
0107             if (left || n == 0)         \
0108                 goto __out;         \
0109             offset += len;              \
0110             len = PAGE_SIZE;            \
0111         }                       \
0112     }                           \
0113 __out:                              \
0114     rcu_read_unlock();                  \
0115     i->iov_offset += __off;                 \
0116     n = __off;                      \
0117 }
0118 
0119 #define __iterate_and_advance(i, n, base, len, off, I, K) { \
0120     if (unlikely(i->count < n))             \
0121         n = i->count;                   \
0122     if (likely(n)) {                    \
0123         if (likely(iter_is_ubuf(i))) {          \
0124             void __user *base;          \
0125             size_t len;             \
0126             iterate_buf(i, n, base, len, off,   \
0127                         i->ubuf, (I))   \
0128         } else if (likely(iter_is_iovec(i))) {      \
0129             const struct iovec *iov = i->iov;   \
0130             void __user *base;          \
0131             size_t len;             \
0132             iterate_iovec(i, n, base, len, off, \
0133                         iov, (I))   \
0134             i->nr_segs -= iov - i->iov;     \
0135             i->iov = iov;               \
0136         } else if (iov_iter_is_bvec(i)) {       \
0137             const struct bio_vec *bvec = i->bvec;   \
0138             void *base;             \
0139             size_t len;             \
0140             iterate_bvec(i, n, base, len, off,  \
0141                         bvec, (K))  \
0142             i->nr_segs -= bvec - i->bvec;       \
0143             i->bvec = bvec;             \
0144         } else if (iov_iter_is_kvec(i)) {       \
0145             const struct kvec *kvec = i->kvec;  \
0146             void *base;             \
0147             size_t len;             \
0148             iterate_iovec(i, n, base, len, off, \
0149                         kvec, (K))  \
0150             i->nr_segs -= kvec - i->kvec;       \
0151             i->kvec = kvec;             \
0152         } else if (iov_iter_is_xarray(i)) {     \
0153             void *base;             \
0154             size_t len;             \
0155             iterate_xarray(i, n, base, len, off,    \
0156                             (K))    \
0157         }                       \
0158         i->count -= n;                  \
0159     }                           \
0160 }
0161 #define iterate_and_advance(i, n, base, len, off, I, K) \
0162     __iterate_and_advance(i, n, base, len, off, I, ((void)(K),0))
0163 
0164 static int copyout(void __user *to, const void *from, size_t n)
0165 {
0166     if (should_fail_usercopy())
0167         return n;
0168     if (access_ok(to, n)) {
0169         instrument_copy_to_user(to, from, n);
0170         n = raw_copy_to_user(to, from, n);
0171     }
0172     return n;
0173 }
0174 
0175 static int copyin(void *to, const void __user *from, size_t n)
0176 {
0177     if (should_fail_usercopy())
0178         return n;
0179     if (access_ok(from, n)) {
0180         instrument_copy_from_user(to, from, n);
0181         n = raw_copy_from_user(to, from, n);
0182     }
0183     return n;
0184 }
0185 
0186 static inline struct pipe_buffer *pipe_buf(const struct pipe_inode_info *pipe,
0187                        unsigned int slot)
0188 {
0189     return &pipe->bufs[slot & (pipe->ring_size - 1)];
0190 }
0191 
0192 #ifdef PIPE_PARANOIA
0193 static bool sanity(const struct iov_iter *i)
0194 {
0195     struct pipe_inode_info *pipe = i->pipe;
0196     unsigned int p_head = pipe->head;
0197     unsigned int p_tail = pipe->tail;
0198     unsigned int p_occupancy = pipe_occupancy(p_head, p_tail);
0199     unsigned int i_head = i->head;
0200     unsigned int idx;
0201 
0202     if (i->last_offset) {
0203         struct pipe_buffer *p;
0204         if (unlikely(p_occupancy == 0))
0205             goto Bad;   // pipe must be non-empty
0206         if (unlikely(i_head != p_head - 1))
0207             goto Bad;   // must be at the last buffer...
0208 
0209         p = pipe_buf(pipe, i_head);
0210         if (unlikely(p->offset + p->len != abs(i->last_offset)))
0211             goto Bad;   // ... at the end of segment
0212     } else {
0213         if (i_head != p_head)
0214             goto Bad;   // must be right after the last buffer
0215     }
0216     return true;
0217 Bad:
0218     printk(KERN_ERR "idx = %d, offset = %d\n", i_head, i->last_offset);
0219     printk(KERN_ERR "head = %d, tail = %d, buffers = %d\n",
0220             p_head, p_tail, pipe->ring_size);
0221     for (idx = 0; idx < pipe->ring_size; idx++)
0222         printk(KERN_ERR "[%p %p %d %d]\n",
0223             pipe->bufs[idx].ops,
0224             pipe->bufs[idx].page,
0225             pipe->bufs[idx].offset,
0226             pipe->bufs[idx].len);
0227     WARN_ON(1);
0228     return false;
0229 }
0230 #else
0231 #define sanity(i) true
0232 #endif
0233 
0234 static struct page *push_anon(struct pipe_inode_info *pipe, unsigned size)
0235 {
0236     struct page *page = alloc_page(GFP_USER);
0237     if (page) {
0238         struct pipe_buffer *buf = pipe_buf(pipe, pipe->head++);
0239         *buf = (struct pipe_buffer) {
0240             .ops = &default_pipe_buf_ops,
0241             .page = page,
0242             .offset = 0,
0243             .len = size
0244         };
0245     }
0246     return page;
0247 }
0248 
0249 static void push_page(struct pipe_inode_info *pipe, struct page *page,
0250             unsigned int offset, unsigned int size)
0251 {
0252     struct pipe_buffer *buf = pipe_buf(pipe, pipe->head++);
0253     *buf = (struct pipe_buffer) {
0254         .ops = &page_cache_pipe_buf_ops,
0255         .page = page,
0256         .offset = offset,
0257         .len = size
0258     };
0259     get_page(page);
0260 }
0261 
0262 static inline int last_offset(const struct pipe_buffer *buf)
0263 {
0264     if (buf->ops == &default_pipe_buf_ops)
0265         return buf->len;    // buf->offset is 0 for those
0266     else
0267         return -(buf->offset + buf->len);
0268 }
0269 
0270 static struct page *append_pipe(struct iov_iter *i, size_t size,
0271                 unsigned int *off)
0272 {
0273     struct pipe_inode_info *pipe = i->pipe;
0274     int offset = i->last_offset;
0275     struct pipe_buffer *buf;
0276     struct page *page;
0277 
0278     if (offset > 0 && offset < PAGE_SIZE) {
0279         // some space in the last buffer; add to it
0280         buf = pipe_buf(pipe, pipe->head - 1);
0281         size = min_t(size_t, size, PAGE_SIZE - offset);
0282         buf->len += size;
0283         i->last_offset += size;
0284         i->count -= size;
0285         *off = offset;
0286         return buf->page;
0287     }
0288     // OK, we need a new buffer
0289     *off = 0;
0290     size = min_t(size_t, size, PAGE_SIZE);
0291     if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
0292         return NULL;
0293     page = push_anon(pipe, size);
0294     if (!page)
0295         return NULL;
0296     i->head = pipe->head - 1;
0297     i->last_offset = size;
0298     i->count -= size;
0299     return page;
0300 }
0301 
0302 static size_t copy_page_to_iter_pipe(struct page *page, size_t offset, size_t bytes,
0303              struct iov_iter *i)
0304 {
0305     struct pipe_inode_info *pipe = i->pipe;
0306     unsigned int head = pipe->head;
0307 
0308     if (unlikely(bytes > i->count))
0309         bytes = i->count;
0310 
0311     if (unlikely(!bytes))
0312         return 0;
0313 
0314     if (!sanity(i))
0315         return 0;
0316 
0317     if (offset && i->last_offset == -offset) { // could we merge it?
0318         struct pipe_buffer *buf = pipe_buf(pipe, head - 1);
0319         if (buf->page == page) {
0320             buf->len += bytes;
0321             i->last_offset -= bytes;
0322             i->count -= bytes;
0323             return bytes;
0324         }
0325     }
0326     if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
0327         return 0;
0328 
0329     push_page(pipe, page, offset, bytes);
0330     i->last_offset = -(offset + bytes);
0331     i->head = head;
0332     i->count -= bytes;
0333     return bytes;
0334 }
0335 
0336 /*
0337  * fault_in_iov_iter_readable - fault in iov iterator for reading
0338  * @i: iterator
0339  * @size: maximum length
0340  *
0341  * Fault in one or more iovecs of the given iov_iter, to a maximum length of
0342  * @size.  For each iovec, fault in each page that constitutes the iovec.
0343  *
0344  * Returns the number of bytes not faulted in (like copy_to_user() and
0345  * copy_from_user()).
0346  *
0347  * Always returns 0 for non-userspace iterators.
0348  */
0349 size_t fault_in_iov_iter_readable(const struct iov_iter *i, size_t size)
0350 {
0351     if (iter_is_ubuf(i)) {
0352         size_t n = min(size, iov_iter_count(i));
0353         n -= fault_in_readable(i->ubuf + i->iov_offset, n);
0354         return size - n;
0355     } else if (iter_is_iovec(i)) {
0356         size_t count = min(size, iov_iter_count(i));
0357         const struct iovec *p;
0358         size_t skip;
0359 
0360         size -= count;
0361         for (p = i->iov, skip = i->iov_offset; count; p++, skip = 0) {
0362             size_t len = min(count, p->iov_len - skip);
0363             size_t ret;
0364 
0365             if (unlikely(!len))
0366                 continue;
0367             ret = fault_in_readable(p->iov_base + skip, len);
0368             count -= len - ret;
0369             if (ret)
0370                 break;
0371         }
0372         return count + size;
0373     }
0374     return 0;
0375 }
0376 EXPORT_SYMBOL(fault_in_iov_iter_readable);
0377 
0378 /*
0379  * fault_in_iov_iter_writeable - fault in iov iterator for writing
0380  * @i: iterator
0381  * @size: maximum length
0382  *
0383  * Faults in the iterator using get_user_pages(), i.e., without triggering
0384  * hardware page faults.  This is primarily useful when we already know that
0385  * some or all of the pages in @i aren't in memory.
0386  *
0387  * Returns the number of bytes not faulted in, like copy_to_user() and
0388  * copy_from_user().
0389  *
0390  * Always returns 0 for non-user-space iterators.
0391  */
0392 size_t fault_in_iov_iter_writeable(const struct iov_iter *i, size_t size)
0393 {
0394     if (iter_is_ubuf(i)) {
0395         size_t n = min(size, iov_iter_count(i));
0396         n -= fault_in_safe_writeable(i->ubuf + i->iov_offset, n);
0397         return size - n;
0398     } else if (iter_is_iovec(i)) {
0399         size_t count = min(size, iov_iter_count(i));
0400         const struct iovec *p;
0401         size_t skip;
0402 
0403         size -= count;
0404         for (p = i->iov, skip = i->iov_offset; count; p++, skip = 0) {
0405             size_t len = min(count, p->iov_len - skip);
0406             size_t ret;
0407 
0408             if (unlikely(!len))
0409                 continue;
0410             ret = fault_in_safe_writeable(p->iov_base + skip, len);
0411             count -= len - ret;
0412             if (ret)
0413                 break;
0414         }
0415         return count + size;
0416     }
0417     return 0;
0418 }
0419 EXPORT_SYMBOL(fault_in_iov_iter_writeable);
0420 
0421 void iov_iter_init(struct iov_iter *i, unsigned int direction,
0422             const struct iovec *iov, unsigned long nr_segs,
0423             size_t count)
0424 {
0425     WARN_ON(direction & ~(READ | WRITE));
0426     *i = (struct iov_iter) {
0427         .iter_type = ITER_IOVEC,
0428         .nofault = false,
0429         .user_backed = true,
0430         .data_source = direction,
0431         .iov = iov,
0432         .nr_segs = nr_segs,
0433         .iov_offset = 0,
0434         .count = count
0435     };
0436 }
0437 EXPORT_SYMBOL(iov_iter_init);
0438 
0439 // returns the offset in partial buffer (if any)
0440 static inline unsigned int pipe_npages(const struct iov_iter *i, int *npages)
0441 {
0442     struct pipe_inode_info *pipe = i->pipe;
0443     int used = pipe->head - pipe->tail;
0444     int off = i->last_offset;
0445 
0446     *npages = max((int)pipe->max_usage - used, 0);
0447 
0448     if (off > 0 && off < PAGE_SIZE) { // anon and not full
0449         (*npages)++;
0450         return off;
0451     }
0452     return 0;
0453 }
0454 
0455 static size_t copy_pipe_to_iter(const void *addr, size_t bytes,
0456                 struct iov_iter *i)
0457 {
0458     unsigned int off, chunk;
0459 
0460     if (unlikely(bytes > i->count))
0461         bytes = i->count;
0462     if (unlikely(!bytes))
0463         return 0;
0464 
0465     if (!sanity(i))
0466         return 0;
0467 
0468     for (size_t n = bytes; n; n -= chunk) {
0469         struct page *page = append_pipe(i, n, &off);
0470         chunk = min_t(size_t, n, PAGE_SIZE - off);
0471         if (!page)
0472             return bytes - n;
0473         memcpy_to_page(page, off, addr, chunk);
0474         addr += chunk;
0475     }
0476     return bytes;
0477 }
0478 
0479 static __wsum csum_and_memcpy(void *to, const void *from, size_t len,
0480                   __wsum sum, size_t off)
0481 {
0482     __wsum next = csum_partial_copy_nocheck(from, to, len);
0483     return csum_block_add(sum, next, off);
0484 }
0485 
0486 static size_t csum_and_copy_to_pipe_iter(const void *addr, size_t bytes,
0487                      struct iov_iter *i, __wsum *sump)
0488 {
0489     __wsum sum = *sump;
0490     size_t off = 0;
0491     unsigned int chunk, r;
0492 
0493     if (unlikely(bytes > i->count))
0494         bytes = i->count;
0495     if (unlikely(!bytes))
0496         return 0;
0497 
0498     if (!sanity(i))
0499         return 0;
0500 
0501     while (bytes) {
0502         struct page *page = append_pipe(i, bytes, &r);
0503         char *p;
0504 
0505         if (!page)
0506             break;
0507         chunk = min_t(size_t, bytes, PAGE_SIZE - r);
0508         p = kmap_local_page(page);
0509         sum = csum_and_memcpy(p + r, addr + off, chunk, sum, off);
0510         kunmap_local(p);
0511         off += chunk;
0512         bytes -= chunk;
0513     }
0514     *sump = sum;
0515     return off;
0516 }
0517 
0518 size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
0519 {
0520     if (unlikely(iov_iter_is_pipe(i)))
0521         return copy_pipe_to_iter(addr, bytes, i);
0522     if (user_backed_iter(i))
0523         might_fault();
0524     iterate_and_advance(i, bytes, base, len, off,
0525         copyout(base, addr + off, len),
0526         memcpy(base, addr + off, len)
0527     )
0528 
0529     return bytes;
0530 }
0531 EXPORT_SYMBOL(_copy_to_iter);
0532 
0533 #ifdef CONFIG_ARCH_HAS_COPY_MC
0534 static int copyout_mc(void __user *to, const void *from, size_t n)
0535 {
0536     if (access_ok(to, n)) {
0537         instrument_copy_to_user(to, from, n);
0538         n = copy_mc_to_user((__force void *) to, from, n);
0539     }
0540     return n;
0541 }
0542 
0543 static size_t copy_mc_pipe_to_iter(const void *addr, size_t bytes,
0544                 struct iov_iter *i)
0545 {
0546     size_t xfer = 0;
0547     unsigned int off, chunk;
0548 
0549     if (unlikely(bytes > i->count))
0550         bytes = i->count;
0551     if (unlikely(!bytes))
0552         return 0;
0553 
0554     if (!sanity(i))
0555         return 0;
0556 
0557     while (bytes) {
0558         struct page *page = append_pipe(i, bytes, &off);
0559         unsigned long rem;
0560         char *p;
0561 
0562         if (!page)
0563             break;
0564         chunk = min_t(size_t, bytes, PAGE_SIZE - off);
0565         p = kmap_local_page(page);
0566         rem = copy_mc_to_kernel(p + off, addr + xfer, chunk);
0567         chunk -= rem;
0568         kunmap_local(p);
0569         xfer += chunk;
0570         bytes -= chunk;
0571         if (rem) {
0572             iov_iter_revert(i, rem);
0573             break;
0574         }
0575     }
0576     return xfer;
0577 }
0578 
0579 /**
0580  * _copy_mc_to_iter - copy to iter with source memory error exception handling
0581  * @addr: source kernel address
0582  * @bytes: total transfer length
0583  * @i: destination iterator
0584  *
0585  * The pmem driver deploys this for the dax operation
0586  * (dax_copy_to_iter()) for dax reads (bypass page-cache and the
0587  * block-layer). Upon #MC read(2) aborts and returns EIO or the bytes
0588  * successfully copied.
0589  *
0590  * The main differences between this and typical _copy_to_iter().
0591  *
0592  * * Typical tail/residue handling after a fault retries the copy
0593  *   byte-by-byte until the fault happens again. Re-triggering machine
0594  *   checks is potentially fatal so the implementation uses source
0595  *   alignment and poison alignment assumptions to avoid re-triggering
0596  *   hardware exceptions.
0597  *
0598  * * ITER_KVEC, ITER_PIPE, and ITER_BVEC can return short copies.
0599  *   Compare to copy_to_iter() where only ITER_IOVEC attempts might return
0600  *   a short copy.
0601  *
0602  * Return: number of bytes copied (may be %0)
0603  */
0604 size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
0605 {
0606     if (unlikely(iov_iter_is_pipe(i)))
0607         return copy_mc_pipe_to_iter(addr, bytes, i);
0608     if (user_backed_iter(i))
0609         might_fault();
0610     __iterate_and_advance(i, bytes, base, len, off,
0611         copyout_mc(base, addr + off, len),
0612         copy_mc_to_kernel(base, addr + off, len)
0613     )
0614 
0615     return bytes;
0616 }
0617 EXPORT_SYMBOL_GPL(_copy_mc_to_iter);
0618 #endif /* CONFIG_ARCH_HAS_COPY_MC */
0619 
0620 size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
0621 {
0622     if (unlikely(iov_iter_is_pipe(i))) {
0623         WARN_ON(1);
0624         return 0;
0625     }
0626     if (user_backed_iter(i))
0627         might_fault();
0628     iterate_and_advance(i, bytes, base, len, off,
0629         copyin(addr + off, base, len),
0630         memcpy(addr + off, base, len)
0631     )
0632 
0633     return bytes;
0634 }
0635 EXPORT_SYMBOL(_copy_from_iter);
0636 
0637 size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
0638 {
0639     if (unlikely(iov_iter_is_pipe(i))) {
0640         WARN_ON(1);
0641         return 0;
0642     }
0643     iterate_and_advance(i, bytes, base, len, off,
0644         __copy_from_user_inatomic_nocache(addr + off, base, len),
0645         memcpy(addr + off, base, len)
0646     )
0647 
0648     return bytes;
0649 }
0650 EXPORT_SYMBOL(_copy_from_iter_nocache);
0651 
0652 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
0653 /**
0654  * _copy_from_iter_flushcache - write destination through cpu cache
0655  * @addr: destination kernel address
0656  * @bytes: total transfer length
0657  * @i: source iterator
0658  *
0659  * The pmem driver arranges for filesystem-dax to use this facility via
0660  * dax_copy_from_iter() for ensuring that writes to persistent memory
0661  * are flushed through the CPU cache. It is differentiated from
0662  * _copy_from_iter_nocache() in that guarantees all data is flushed for
0663  * all iterator types. The _copy_from_iter_nocache() only attempts to
0664  * bypass the cache for the ITER_IOVEC case, and on some archs may use
0665  * instructions that strand dirty-data in the cache.
0666  *
0667  * Return: number of bytes copied (may be %0)
0668  */
0669 size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
0670 {
0671     if (unlikely(iov_iter_is_pipe(i))) {
0672         WARN_ON(1);
0673         return 0;
0674     }
0675     iterate_and_advance(i, bytes, base, len, off,
0676         __copy_from_user_flushcache(addr + off, base, len),
0677         memcpy_flushcache(addr + off, base, len)
0678     )
0679 
0680     return bytes;
0681 }
0682 EXPORT_SYMBOL_GPL(_copy_from_iter_flushcache);
0683 #endif
0684 
0685 static inline bool page_copy_sane(struct page *page, size_t offset, size_t n)
0686 {
0687     struct page *head;
0688     size_t v = n + offset;
0689 
0690     /*
0691      * The general case needs to access the page order in order
0692      * to compute the page size.
0693      * However, we mostly deal with order-0 pages and thus can
0694      * avoid a possible cache line miss for requests that fit all
0695      * page orders.
0696      */
0697     if (n <= v && v <= PAGE_SIZE)
0698         return true;
0699 
0700     head = compound_head(page);
0701     v += (page - head) << PAGE_SHIFT;
0702 
0703     if (likely(n <= v && v <= (page_size(head))))
0704         return true;
0705     WARN_ON(1);
0706     return false;
0707 }
0708 
0709 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
0710              struct iov_iter *i)
0711 {
0712     size_t res = 0;
0713     if (unlikely(!page_copy_sane(page, offset, bytes)))
0714         return 0;
0715     if (unlikely(iov_iter_is_pipe(i)))
0716         return copy_page_to_iter_pipe(page, offset, bytes, i);
0717     page += offset / PAGE_SIZE; // first subpage
0718     offset %= PAGE_SIZE;
0719     while (1) {
0720         void *kaddr = kmap_local_page(page);
0721         size_t n = min(bytes, (size_t)PAGE_SIZE - offset);
0722         n = _copy_to_iter(kaddr + offset, n, i);
0723         kunmap_local(kaddr);
0724         res += n;
0725         bytes -= n;
0726         if (!bytes || !n)
0727             break;
0728         offset += n;
0729         if (offset == PAGE_SIZE) {
0730             page++;
0731             offset = 0;
0732         }
0733     }
0734     return res;
0735 }
0736 EXPORT_SYMBOL(copy_page_to_iter);
0737 
0738 size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
0739              struct iov_iter *i)
0740 {
0741     size_t res = 0;
0742     if (!page_copy_sane(page, offset, bytes))
0743         return 0;
0744     page += offset / PAGE_SIZE; // first subpage
0745     offset %= PAGE_SIZE;
0746     while (1) {
0747         void *kaddr = kmap_local_page(page);
0748         size_t n = min(bytes, (size_t)PAGE_SIZE - offset);
0749         n = _copy_from_iter(kaddr + offset, n, i);
0750         kunmap_local(kaddr);
0751         res += n;
0752         bytes -= n;
0753         if (!bytes || !n)
0754             break;
0755         offset += n;
0756         if (offset == PAGE_SIZE) {
0757             page++;
0758             offset = 0;
0759         }
0760     }
0761     return res;
0762 }
0763 EXPORT_SYMBOL(copy_page_from_iter);
0764 
0765 static size_t pipe_zero(size_t bytes, struct iov_iter *i)
0766 {
0767     unsigned int chunk, off;
0768 
0769     if (unlikely(bytes > i->count))
0770         bytes = i->count;
0771     if (unlikely(!bytes))
0772         return 0;
0773 
0774     if (!sanity(i))
0775         return 0;
0776 
0777     for (size_t n = bytes; n; n -= chunk) {
0778         struct page *page = append_pipe(i, n, &off);
0779         char *p;
0780 
0781         if (!page)
0782             return bytes - n;
0783         chunk = min_t(size_t, n, PAGE_SIZE - off);
0784         p = kmap_local_page(page);
0785         memset(p + off, 0, chunk);
0786         kunmap_local(p);
0787     }
0788     return bytes;
0789 }
0790 
0791 size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
0792 {
0793     if (unlikely(iov_iter_is_pipe(i)))
0794         return pipe_zero(bytes, i);
0795     iterate_and_advance(i, bytes, base, len, count,
0796         clear_user(base, len),
0797         memset(base, 0, len)
0798     )
0799 
0800     return bytes;
0801 }
0802 EXPORT_SYMBOL(iov_iter_zero);
0803 
0804 size_t copy_page_from_iter_atomic(struct page *page, unsigned offset, size_t bytes,
0805                   struct iov_iter *i)
0806 {
0807     char *kaddr = kmap_atomic(page), *p = kaddr + offset;
0808     if (unlikely(!page_copy_sane(page, offset, bytes))) {
0809         kunmap_atomic(kaddr);
0810         return 0;
0811     }
0812     if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {
0813         kunmap_atomic(kaddr);
0814         WARN_ON(1);
0815         return 0;
0816     }
0817     iterate_and_advance(i, bytes, base, len, off,
0818         copyin(p + off, base, len),
0819         memcpy(p + off, base, len)
0820     )
0821     kunmap_atomic(kaddr);
0822     return bytes;
0823 }
0824 EXPORT_SYMBOL(copy_page_from_iter_atomic);
0825 
0826 static void pipe_advance(struct iov_iter *i, size_t size)
0827 {
0828     struct pipe_inode_info *pipe = i->pipe;
0829     int off = i->last_offset;
0830 
0831     if (!off && !size) {
0832         pipe_discard_from(pipe, i->start_head); // discard everything
0833         return;
0834     }
0835     i->count -= size;
0836     while (1) {
0837         struct pipe_buffer *buf = pipe_buf(pipe, i->head);
0838         if (off) /* make it relative to the beginning of buffer */
0839             size += abs(off) - buf->offset;
0840         if (size <= buf->len) {
0841             buf->len = size;
0842             i->last_offset = last_offset(buf);
0843             break;
0844         }
0845         size -= buf->len;
0846         i->head++;
0847         off = 0;
0848     }
0849     pipe_discard_from(pipe, i->head + 1); // discard everything past this one
0850 }
0851 
0852 static void iov_iter_bvec_advance(struct iov_iter *i, size_t size)
0853 {
0854     const struct bio_vec *bvec, *end;
0855 
0856     if (!i->count)
0857         return;
0858     i->count -= size;
0859 
0860     size += i->iov_offset;
0861 
0862     for (bvec = i->bvec, end = bvec + i->nr_segs; bvec < end; bvec++) {
0863         if (likely(size < bvec->bv_len))
0864             break;
0865         size -= bvec->bv_len;
0866     }
0867     i->iov_offset = size;
0868     i->nr_segs -= bvec - i->bvec;
0869     i->bvec = bvec;
0870 }
0871 
0872 static void iov_iter_iovec_advance(struct iov_iter *i, size_t size)
0873 {
0874     const struct iovec *iov, *end;
0875 
0876     if (!i->count)
0877         return;
0878     i->count -= size;
0879 
0880     size += i->iov_offset; // from beginning of current segment
0881     for (iov = i->iov, end = iov + i->nr_segs; iov < end; iov++) {
0882         if (likely(size < iov->iov_len))
0883             break;
0884         size -= iov->iov_len;
0885     }
0886     i->iov_offset = size;
0887     i->nr_segs -= iov - i->iov;
0888     i->iov = iov;
0889 }
0890 
0891 void iov_iter_advance(struct iov_iter *i, size_t size)
0892 {
0893     if (unlikely(i->count < size))
0894         size = i->count;
0895     if (likely(iter_is_ubuf(i)) || unlikely(iov_iter_is_xarray(i))) {
0896         i->iov_offset += size;
0897         i->count -= size;
0898     } else if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i))) {
0899         /* iovec and kvec have identical layouts */
0900         iov_iter_iovec_advance(i, size);
0901     } else if (iov_iter_is_bvec(i)) {
0902         iov_iter_bvec_advance(i, size);
0903     } else if (iov_iter_is_pipe(i)) {
0904         pipe_advance(i, size);
0905     } else if (iov_iter_is_discard(i)) {
0906         i->count -= size;
0907     }
0908 }
0909 EXPORT_SYMBOL(iov_iter_advance);
0910 
0911 void iov_iter_revert(struct iov_iter *i, size_t unroll)
0912 {
0913     if (!unroll)
0914         return;
0915     if (WARN_ON(unroll > MAX_RW_COUNT))
0916         return;
0917     i->count += unroll;
0918     if (unlikely(iov_iter_is_pipe(i))) {
0919         struct pipe_inode_info *pipe = i->pipe;
0920         unsigned int head = pipe->head;
0921 
0922         while (head > i->start_head) {
0923             struct pipe_buffer *b = pipe_buf(pipe, --head);
0924             if (unroll < b->len) {
0925                 b->len -= unroll;
0926                 i->last_offset = last_offset(b);
0927                 i->head = head;
0928                 return;
0929             }
0930             unroll -= b->len;
0931             pipe_buf_release(pipe, b);
0932             pipe->head--;
0933         }
0934         i->last_offset = 0;
0935         i->head = head;
0936         return;
0937     }
0938     if (unlikely(iov_iter_is_discard(i)))
0939         return;
0940     if (unroll <= i->iov_offset) {
0941         i->iov_offset -= unroll;
0942         return;
0943     }
0944     unroll -= i->iov_offset;
0945     if (iov_iter_is_xarray(i) || iter_is_ubuf(i)) {
0946         BUG(); /* We should never go beyond the start of the specified
0947             * range since we might then be straying into pages that
0948             * aren't pinned.
0949             */
0950     } else if (iov_iter_is_bvec(i)) {
0951         const struct bio_vec *bvec = i->bvec;
0952         while (1) {
0953             size_t n = (--bvec)->bv_len;
0954             i->nr_segs++;
0955             if (unroll <= n) {
0956                 i->bvec = bvec;
0957                 i->iov_offset = n - unroll;
0958                 return;
0959             }
0960             unroll -= n;
0961         }
0962     } else { /* same logics for iovec and kvec */
0963         const struct iovec *iov = i->iov;
0964         while (1) {
0965             size_t n = (--iov)->iov_len;
0966             i->nr_segs++;
0967             if (unroll <= n) {
0968                 i->iov = iov;
0969                 i->iov_offset = n - unroll;
0970                 return;
0971             }
0972             unroll -= n;
0973         }
0974     }
0975 }
0976 EXPORT_SYMBOL(iov_iter_revert);
0977 
0978 /*
0979  * Return the count of just the current iov_iter segment.
0980  */
0981 size_t iov_iter_single_seg_count(const struct iov_iter *i)
0982 {
0983     if (i->nr_segs > 1) {
0984         if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
0985             return min(i->count, i->iov->iov_len - i->iov_offset);
0986         if (iov_iter_is_bvec(i))
0987             return min(i->count, i->bvec->bv_len - i->iov_offset);
0988     }
0989     return i->count;
0990 }
0991 EXPORT_SYMBOL(iov_iter_single_seg_count);
0992 
0993 void iov_iter_kvec(struct iov_iter *i, unsigned int direction,
0994             const struct kvec *kvec, unsigned long nr_segs,
0995             size_t count)
0996 {
0997     WARN_ON(direction & ~(READ | WRITE));
0998     *i = (struct iov_iter){
0999         .iter_type = ITER_KVEC,
1000         .data_source = direction,
1001         .kvec = kvec,
1002         .nr_segs = nr_segs,
1003         .iov_offset = 0,
1004         .count = count
1005     };
1006 }
1007 EXPORT_SYMBOL(iov_iter_kvec);
1008 
1009 void iov_iter_bvec(struct iov_iter *i, unsigned int direction,
1010             const struct bio_vec *bvec, unsigned long nr_segs,
1011             size_t count)
1012 {
1013     WARN_ON(direction & ~(READ | WRITE));
1014     *i = (struct iov_iter){
1015         .iter_type = ITER_BVEC,
1016         .data_source = direction,
1017         .bvec = bvec,
1018         .nr_segs = nr_segs,
1019         .iov_offset = 0,
1020         .count = count
1021     };
1022 }
1023 EXPORT_SYMBOL(iov_iter_bvec);
1024 
1025 void iov_iter_pipe(struct iov_iter *i, unsigned int direction,
1026             struct pipe_inode_info *pipe,
1027             size_t count)
1028 {
1029     BUG_ON(direction != READ);
1030     WARN_ON(pipe_full(pipe->head, pipe->tail, pipe->ring_size));
1031     *i = (struct iov_iter){
1032         .iter_type = ITER_PIPE,
1033         .data_source = false,
1034         .pipe = pipe,
1035         .head = pipe->head,
1036         .start_head = pipe->head,
1037         .last_offset = 0,
1038         .count = count
1039     };
1040 }
1041 EXPORT_SYMBOL(iov_iter_pipe);
1042 
1043 /**
1044  * iov_iter_xarray - Initialise an I/O iterator to use the pages in an xarray
1045  * @i: The iterator to initialise.
1046  * @direction: The direction of the transfer.
1047  * @xarray: The xarray to access.
1048  * @start: The start file position.
1049  * @count: The size of the I/O buffer in bytes.
1050  *
1051  * Set up an I/O iterator to either draw data out of the pages attached to an
1052  * inode or to inject data into those pages.  The pages *must* be prevented
1053  * from evaporation, either by taking a ref on them or locking them by the
1054  * caller.
1055  */
1056 void iov_iter_xarray(struct iov_iter *i, unsigned int direction,
1057              struct xarray *xarray, loff_t start, size_t count)
1058 {
1059     BUG_ON(direction & ~1);
1060     *i = (struct iov_iter) {
1061         .iter_type = ITER_XARRAY,
1062         .data_source = direction,
1063         .xarray = xarray,
1064         .xarray_start = start,
1065         .count = count,
1066         .iov_offset = 0
1067     };
1068 }
1069 EXPORT_SYMBOL(iov_iter_xarray);
1070 
1071 /**
1072  * iov_iter_discard - Initialise an I/O iterator that discards data
1073  * @i: The iterator to initialise.
1074  * @direction: The direction of the transfer.
1075  * @count: The size of the I/O buffer in bytes.
1076  *
1077  * Set up an I/O iterator that just discards everything that's written to it.
1078  * It's only available as a READ iterator.
1079  */
1080 void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count)
1081 {
1082     BUG_ON(direction != READ);
1083     *i = (struct iov_iter){
1084         .iter_type = ITER_DISCARD,
1085         .data_source = false,
1086         .count = count,
1087         .iov_offset = 0
1088     };
1089 }
1090 EXPORT_SYMBOL(iov_iter_discard);
1091 
1092 static bool iov_iter_aligned_iovec(const struct iov_iter *i, unsigned addr_mask,
1093                    unsigned len_mask)
1094 {
1095     size_t size = i->count;
1096     size_t skip = i->iov_offset;
1097     unsigned k;
1098 
1099     for (k = 0; k < i->nr_segs; k++, skip = 0) {
1100         size_t len = i->iov[k].iov_len - skip;
1101 
1102         if (len > size)
1103             len = size;
1104         if (len & len_mask)
1105             return false;
1106         if ((unsigned long)(i->iov[k].iov_base + skip) & addr_mask)
1107             return false;
1108 
1109         size -= len;
1110         if (!size)
1111             break;
1112     }
1113     return true;
1114 }
1115 
1116 static bool iov_iter_aligned_bvec(const struct iov_iter *i, unsigned addr_mask,
1117                   unsigned len_mask)
1118 {
1119     size_t size = i->count;
1120     unsigned skip = i->iov_offset;
1121     unsigned k;
1122 
1123     for (k = 0; k < i->nr_segs; k++, skip = 0) {
1124         size_t len = i->bvec[k].bv_len - skip;
1125 
1126         if (len > size)
1127             len = size;
1128         if (len & len_mask)
1129             return false;
1130         if ((unsigned long)(i->bvec[k].bv_offset + skip) & addr_mask)
1131             return false;
1132 
1133         size -= len;
1134         if (!size)
1135             break;
1136     }
1137     return true;
1138 }
1139 
1140 /**
1141  * iov_iter_is_aligned() - Check if the addresses and lengths of each segments
1142  *  are aligned to the parameters.
1143  *
1144  * @i: &struct iov_iter to restore
1145  * @addr_mask: bit mask to check against the iov element's addresses
1146  * @len_mask: bit mask to check against the iov element's lengths
1147  *
1148  * Return: false if any addresses or lengths intersect with the provided masks
1149  */
1150 bool iov_iter_is_aligned(const struct iov_iter *i, unsigned addr_mask,
1151              unsigned len_mask)
1152 {
1153     if (likely(iter_is_ubuf(i))) {
1154         if (i->count & len_mask)
1155             return false;
1156         if ((unsigned long)(i->ubuf + i->iov_offset) & addr_mask)
1157             return false;
1158         return true;
1159     }
1160 
1161     if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
1162         return iov_iter_aligned_iovec(i, addr_mask, len_mask);
1163 
1164     if (iov_iter_is_bvec(i))
1165         return iov_iter_aligned_bvec(i, addr_mask, len_mask);
1166 
1167     if (iov_iter_is_pipe(i)) {
1168         size_t size = i->count;
1169 
1170         if (size & len_mask)
1171             return false;
1172         if (size && i->last_offset > 0) {
1173             if (i->last_offset & addr_mask)
1174                 return false;
1175         }
1176 
1177         return true;
1178     }
1179 
1180     if (iov_iter_is_xarray(i)) {
1181         if (i->count & len_mask)
1182             return false;
1183         if ((i->xarray_start + i->iov_offset) & addr_mask)
1184             return false;
1185     }
1186 
1187     return true;
1188 }
1189 EXPORT_SYMBOL_GPL(iov_iter_is_aligned);
1190 
1191 static unsigned long iov_iter_alignment_iovec(const struct iov_iter *i)
1192 {
1193     unsigned long res = 0;
1194     size_t size = i->count;
1195     size_t skip = i->iov_offset;
1196     unsigned k;
1197 
1198     for (k = 0; k < i->nr_segs; k++, skip = 0) {
1199         size_t len = i->iov[k].iov_len - skip;
1200         if (len) {
1201             res |= (unsigned long)i->iov[k].iov_base + skip;
1202             if (len > size)
1203                 len = size;
1204             res |= len;
1205             size -= len;
1206             if (!size)
1207                 break;
1208         }
1209     }
1210     return res;
1211 }
1212 
1213 static unsigned long iov_iter_alignment_bvec(const struct iov_iter *i)
1214 {
1215     unsigned res = 0;
1216     size_t size = i->count;
1217     unsigned skip = i->iov_offset;
1218     unsigned k;
1219 
1220     for (k = 0; k < i->nr_segs; k++, skip = 0) {
1221         size_t len = i->bvec[k].bv_len - skip;
1222         res |= (unsigned long)i->bvec[k].bv_offset + skip;
1223         if (len > size)
1224             len = size;
1225         res |= len;
1226         size -= len;
1227         if (!size)
1228             break;
1229     }
1230     return res;
1231 }
1232 
1233 unsigned long iov_iter_alignment(const struct iov_iter *i)
1234 {
1235     if (likely(iter_is_ubuf(i))) {
1236         size_t size = i->count;
1237         if (size)
1238             return ((unsigned long)i->ubuf + i->iov_offset) | size;
1239         return 0;
1240     }
1241 
1242     /* iovec and kvec have identical layouts */
1243     if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
1244         return iov_iter_alignment_iovec(i);
1245 
1246     if (iov_iter_is_bvec(i))
1247         return iov_iter_alignment_bvec(i);
1248 
1249     if (iov_iter_is_pipe(i)) {
1250         size_t size = i->count;
1251 
1252         if (size && i->last_offset > 0)
1253             return size | i->last_offset;
1254         return size;
1255     }
1256 
1257     if (iov_iter_is_xarray(i))
1258         return (i->xarray_start + i->iov_offset) | i->count;
1259 
1260     return 0;
1261 }
1262 EXPORT_SYMBOL(iov_iter_alignment);
1263 
1264 unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
1265 {
1266     unsigned long res = 0;
1267     unsigned long v = 0;
1268     size_t size = i->count;
1269     unsigned k;
1270 
1271     if (iter_is_ubuf(i))
1272         return 0;
1273 
1274     if (WARN_ON(!iter_is_iovec(i)))
1275         return ~0U;
1276 
1277     for (k = 0; k < i->nr_segs; k++) {
1278         if (i->iov[k].iov_len) {
1279             unsigned long base = (unsigned long)i->iov[k].iov_base;
1280             if (v) // if not the first one
1281                 res |= base | v; // this start | previous end
1282             v = base + i->iov[k].iov_len;
1283             if (size <= i->iov[k].iov_len)
1284                 break;
1285             size -= i->iov[k].iov_len;
1286         }
1287     }
1288     return res;
1289 }
1290 EXPORT_SYMBOL(iov_iter_gap_alignment);
1291 
1292 static int want_pages_array(struct page ***res, size_t size,
1293                 size_t start, unsigned int maxpages)
1294 {
1295     unsigned int count = DIV_ROUND_UP(size + start, PAGE_SIZE);
1296 
1297     if (count > maxpages)
1298         count = maxpages;
1299     WARN_ON(!count);    // caller should've prevented that
1300     if (!*res) {
1301         *res = kvmalloc_array(count, sizeof(struct page *), GFP_KERNEL);
1302         if (!*res)
1303             return 0;
1304     }
1305     return count;
1306 }
1307 
1308 static ssize_t pipe_get_pages(struct iov_iter *i,
1309            struct page ***pages, size_t maxsize, unsigned maxpages,
1310            size_t *start)
1311 {
1312     unsigned int npages, count, off, chunk;
1313     struct page **p;
1314     size_t left;
1315 
1316     if (!sanity(i))
1317         return -EFAULT;
1318 
1319     *start = off = pipe_npages(i, &npages);
1320     if (!npages)
1321         return -EFAULT;
1322     count = want_pages_array(pages, maxsize, off, min(npages, maxpages));
1323     if (!count)
1324         return -ENOMEM;
1325     p = *pages;
1326     for (npages = 0, left = maxsize ; npages < count; npages++, left -= chunk) {
1327         struct page *page = append_pipe(i, left, &off);
1328         if (!page)
1329             break;
1330         chunk = min_t(size_t, left, PAGE_SIZE - off);
1331         get_page(*p++ = page);
1332     }
1333     if (!npages)
1334         return -EFAULT;
1335     return maxsize - left;
1336 }
1337 
1338 static ssize_t iter_xarray_populate_pages(struct page **pages, struct xarray *xa,
1339                       pgoff_t index, unsigned int nr_pages)
1340 {
1341     XA_STATE(xas, xa, index);
1342     struct page *page;
1343     unsigned int ret = 0;
1344 
1345     rcu_read_lock();
1346     for (page = xas_load(&xas); page; page = xas_next(&xas)) {
1347         if (xas_retry(&xas, page))
1348             continue;
1349 
1350         /* Has the page moved or been split? */
1351         if (unlikely(page != xas_reload(&xas))) {
1352             xas_reset(&xas);
1353             continue;
1354         }
1355 
1356         pages[ret] = find_subpage(page, xas.xa_index);
1357         get_page(pages[ret]);
1358         if (++ret == nr_pages)
1359             break;
1360     }
1361     rcu_read_unlock();
1362     return ret;
1363 }
1364 
1365 static ssize_t iter_xarray_get_pages(struct iov_iter *i,
1366                      struct page ***pages, size_t maxsize,
1367                      unsigned maxpages, size_t *_start_offset)
1368 {
1369     unsigned nr, offset, count;
1370     pgoff_t index;
1371     loff_t pos;
1372 
1373     pos = i->xarray_start + i->iov_offset;
1374     index = pos >> PAGE_SHIFT;
1375     offset = pos & ~PAGE_MASK;
1376     *_start_offset = offset;
1377 
1378     count = want_pages_array(pages, maxsize, offset, maxpages);
1379     if (!count)
1380         return -ENOMEM;
1381     nr = iter_xarray_populate_pages(*pages, i->xarray, index, count);
1382     if (nr == 0)
1383         return 0;
1384 
1385     maxsize = min_t(size_t, nr * PAGE_SIZE - offset, maxsize);
1386     i->iov_offset += maxsize;
1387     i->count -= maxsize;
1388     return maxsize;
1389 }
1390 
1391 /* must be done on non-empty ITER_UBUF or ITER_IOVEC one */
1392 static unsigned long first_iovec_segment(const struct iov_iter *i, size_t *size)
1393 {
1394     size_t skip;
1395     long k;
1396 
1397     if (iter_is_ubuf(i))
1398         return (unsigned long)i->ubuf + i->iov_offset;
1399 
1400     for (k = 0, skip = i->iov_offset; k < i->nr_segs; k++, skip = 0) {
1401         size_t len = i->iov[k].iov_len - skip;
1402 
1403         if (unlikely(!len))
1404             continue;
1405         if (*size > len)
1406             *size = len;
1407         return (unsigned long)i->iov[k].iov_base + skip;
1408     }
1409     BUG(); // if it had been empty, we wouldn't get called
1410 }
1411 
1412 /* must be done on non-empty ITER_BVEC one */
1413 static struct page *first_bvec_segment(const struct iov_iter *i,
1414                        size_t *size, size_t *start)
1415 {
1416     struct page *page;
1417     size_t skip = i->iov_offset, len;
1418 
1419     len = i->bvec->bv_len - skip;
1420     if (*size > len)
1421         *size = len;
1422     skip += i->bvec->bv_offset;
1423     page = i->bvec->bv_page + skip / PAGE_SIZE;
1424     *start = skip % PAGE_SIZE;
1425     return page;
1426 }
1427 
1428 static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
1429            struct page ***pages, size_t maxsize,
1430            unsigned int maxpages, size_t *start)
1431 {
1432     unsigned int n;
1433 
1434     if (maxsize > i->count)
1435         maxsize = i->count;
1436     if (!maxsize)
1437         return 0;
1438     if (maxsize > MAX_RW_COUNT)
1439         maxsize = MAX_RW_COUNT;
1440 
1441     if (likely(user_backed_iter(i))) {
1442         unsigned int gup_flags = 0;
1443         unsigned long addr;
1444         int res;
1445 
1446         if (iov_iter_rw(i) != WRITE)
1447             gup_flags |= FOLL_WRITE;
1448         if (i->nofault)
1449             gup_flags |= FOLL_NOFAULT;
1450 
1451         addr = first_iovec_segment(i, &maxsize);
1452         *start = addr % PAGE_SIZE;
1453         addr &= PAGE_MASK;
1454         n = want_pages_array(pages, maxsize, *start, maxpages);
1455         if (!n)
1456             return -ENOMEM;
1457         res = get_user_pages_fast(addr, n, gup_flags, *pages);
1458         if (unlikely(res <= 0))
1459             return res;
1460         maxsize = min_t(size_t, maxsize, res * PAGE_SIZE - *start);
1461         iov_iter_advance(i, maxsize);
1462         return maxsize;
1463     }
1464     if (iov_iter_is_bvec(i)) {
1465         struct page **p;
1466         struct page *page;
1467 
1468         page = first_bvec_segment(i, &maxsize, start);
1469         n = want_pages_array(pages, maxsize, *start, maxpages);
1470         if (!n)
1471             return -ENOMEM;
1472         p = *pages;
1473         for (int k = 0; k < n; k++)
1474             get_page(p[k] = page + k);
1475         maxsize = min_t(size_t, maxsize, n * PAGE_SIZE - *start);
1476         i->count -= maxsize;
1477         i->iov_offset += maxsize;
1478         if (i->iov_offset == i->bvec->bv_len) {
1479             i->iov_offset = 0;
1480             i->bvec++;
1481             i->nr_segs--;
1482         }
1483         return maxsize;
1484     }
1485     if (iov_iter_is_pipe(i))
1486         return pipe_get_pages(i, pages, maxsize, maxpages, start);
1487     if (iov_iter_is_xarray(i))
1488         return iter_xarray_get_pages(i, pages, maxsize, maxpages, start);
1489     return -EFAULT;
1490 }
1491 
1492 ssize_t iov_iter_get_pages2(struct iov_iter *i,
1493            struct page **pages, size_t maxsize, unsigned maxpages,
1494            size_t *start)
1495 {
1496     if (!maxpages)
1497         return 0;
1498     BUG_ON(!pages);
1499 
1500     return __iov_iter_get_pages_alloc(i, &pages, maxsize, maxpages, start);
1501 }
1502 EXPORT_SYMBOL(iov_iter_get_pages2);
1503 
1504 ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i,
1505            struct page ***pages, size_t maxsize,
1506            size_t *start)
1507 {
1508     ssize_t len;
1509 
1510     *pages = NULL;
1511 
1512     len = __iov_iter_get_pages_alloc(i, pages, maxsize, ~0U, start);
1513     if (len <= 0) {
1514         kvfree(*pages);
1515         *pages = NULL;
1516     }
1517     return len;
1518 }
1519 EXPORT_SYMBOL(iov_iter_get_pages_alloc2);
1520 
1521 size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
1522                    struct iov_iter *i)
1523 {
1524     __wsum sum, next;
1525     sum = *csum;
1526     if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {
1527         WARN_ON(1);
1528         return 0;
1529     }
1530     iterate_and_advance(i, bytes, base, len, off, ({
1531         next = csum_and_copy_from_user(base, addr + off, len);
1532         sum = csum_block_add(sum, next, off);
1533         next ? 0 : len;
1534     }), ({
1535         sum = csum_and_memcpy(addr + off, base, len, sum, off);
1536     })
1537     )
1538     *csum = sum;
1539     return bytes;
1540 }
1541 EXPORT_SYMBOL(csum_and_copy_from_iter);
1542 
1543 size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate,
1544                  struct iov_iter *i)
1545 {
1546     struct csum_state *csstate = _csstate;
1547     __wsum sum, next;
1548 
1549     if (unlikely(iov_iter_is_discard(i))) {
1550         WARN_ON(1); /* for now */
1551         return 0;
1552     }
1553 
1554     sum = csum_shift(csstate->csum, csstate->off);
1555     if (unlikely(iov_iter_is_pipe(i)))
1556         bytes = csum_and_copy_to_pipe_iter(addr, bytes, i, &sum);
1557     else iterate_and_advance(i, bytes, base, len, off, ({
1558         next = csum_and_copy_to_user(addr + off, base, len);
1559         sum = csum_block_add(sum, next, off);
1560         next ? 0 : len;
1561     }), ({
1562         sum = csum_and_memcpy(base, addr + off, len, sum, off);
1563     })
1564     )
1565     csstate->csum = csum_shift(sum, csstate->off);
1566     csstate->off += bytes;
1567     return bytes;
1568 }
1569 EXPORT_SYMBOL(csum_and_copy_to_iter);
1570 
1571 size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
1572         struct iov_iter *i)
1573 {
1574 #ifdef CONFIG_CRYPTO_HASH
1575     struct ahash_request *hash = hashp;
1576     struct scatterlist sg;
1577     size_t copied;
1578 
1579     copied = copy_to_iter(addr, bytes, i);
1580     sg_init_one(&sg, addr, copied);
1581     ahash_request_set_crypt(hash, &sg, NULL, copied);
1582     crypto_ahash_update(hash);
1583     return copied;
1584 #else
1585     return 0;
1586 #endif
1587 }
1588 EXPORT_SYMBOL(hash_and_copy_to_iter);
1589 
1590 static int iov_npages(const struct iov_iter *i, int maxpages)
1591 {
1592     size_t skip = i->iov_offset, size = i->count;
1593     const struct iovec *p;
1594     int npages = 0;
1595 
1596     for (p = i->iov; size; skip = 0, p++) {
1597         unsigned offs = offset_in_page(p->iov_base + skip);
1598         size_t len = min(p->iov_len - skip, size);
1599 
1600         if (len) {
1601             size -= len;
1602             npages += DIV_ROUND_UP(offs + len, PAGE_SIZE);
1603             if (unlikely(npages > maxpages))
1604                 return maxpages;
1605         }
1606     }
1607     return npages;
1608 }
1609 
1610 static int bvec_npages(const struct iov_iter *i, int maxpages)
1611 {
1612     size_t skip = i->iov_offset, size = i->count;
1613     const struct bio_vec *p;
1614     int npages = 0;
1615 
1616     for (p = i->bvec; size; skip = 0, p++) {
1617         unsigned offs = (p->bv_offset + skip) % PAGE_SIZE;
1618         size_t len = min(p->bv_len - skip, size);
1619 
1620         size -= len;
1621         npages += DIV_ROUND_UP(offs + len, PAGE_SIZE);
1622         if (unlikely(npages > maxpages))
1623             return maxpages;
1624     }
1625     return npages;
1626 }
1627 
1628 int iov_iter_npages(const struct iov_iter *i, int maxpages)
1629 {
1630     if (unlikely(!i->count))
1631         return 0;
1632     if (likely(iter_is_ubuf(i))) {
1633         unsigned offs = offset_in_page(i->ubuf + i->iov_offset);
1634         int npages = DIV_ROUND_UP(offs + i->count, PAGE_SIZE);
1635         return min(npages, maxpages);
1636     }
1637     /* iovec and kvec have identical layouts */
1638     if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
1639         return iov_npages(i, maxpages);
1640     if (iov_iter_is_bvec(i))
1641         return bvec_npages(i, maxpages);
1642     if (iov_iter_is_pipe(i)) {
1643         int npages;
1644 
1645         if (!sanity(i))
1646             return 0;
1647 
1648         pipe_npages(i, &npages);
1649         return min(npages, maxpages);
1650     }
1651     if (iov_iter_is_xarray(i)) {
1652         unsigned offset = (i->xarray_start + i->iov_offset) % PAGE_SIZE;
1653         int npages = DIV_ROUND_UP(offset + i->count, PAGE_SIZE);
1654         return min(npages, maxpages);
1655     }
1656     return 0;
1657 }
1658 EXPORT_SYMBOL(iov_iter_npages);
1659 
1660 const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
1661 {
1662     *new = *old;
1663     if (unlikely(iov_iter_is_pipe(new))) {
1664         WARN_ON(1);
1665         return NULL;
1666     }
1667     if (iov_iter_is_bvec(new))
1668         return new->bvec = kmemdup(new->bvec,
1669                     new->nr_segs * sizeof(struct bio_vec),
1670                     flags);
1671     else if (iov_iter_is_kvec(new) || iter_is_iovec(new))
1672         /* iovec and kvec have identical layout */
1673         return new->iov = kmemdup(new->iov,
1674                    new->nr_segs * sizeof(struct iovec),
1675                    flags);
1676     return NULL;
1677 }
1678 EXPORT_SYMBOL(dup_iter);
1679 
1680 static int copy_compat_iovec_from_user(struct iovec *iov,
1681         const struct iovec __user *uvec, unsigned long nr_segs)
1682 {
1683     const struct compat_iovec __user *uiov =
1684         (const struct compat_iovec __user *)uvec;
1685     int ret = -EFAULT, i;
1686 
1687     if (!user_access_begin(uiov, nr_segs * sizeof(*uiov)))
1688         return -EFAULT;
1689 
1690     for (i = 0; i < nr_segs; i++) {
1691         compat_uptr_t buf;
1692         compat_ssize_t len;
1693 
1694         unsafe_get_user(len, &uiov[i].iov_len, uaccess_end);
1695         unsafe_get_user(buf, &uiov[i].iov_base, uaccess_end);
1696 
1697         /* check for compat_size_t not fitting in compat_ssize_t .. */
1698         if (len < 0) {
1699             ret = -EINVAL;
1700             goto uaccess_end;
1701         }
1702         iov[i].iov_base = compat_ptr(buf);
1703         iov[i].iov_len = len;
1704     }
1705 
1706     ret = 0;
1707 uaccess_end:
1708     user_access_end();
1709     return ret;
1710 }
1711 
1712 static int copy_iovec_from_user(struct iovec *iov,
1713         const struct iovec __user *uvec, unsigned long nr_segs)
1714 {
1715     unsigned long seg;
1716 
1717     if (copy_from_user(iov, uvec, nr_segs * sizeof(*uvec)))
1718         return -EFAULT;
1719     for (seg = 0; seg < nr_segs; seg++) {
1720         if ((ssize_t)iov[seg].iov_len < 0)
1721             return -EINVAL;
1722     }
1723 
1724     return 0;
1725 }
1726 
1727 struct iovec *iovec_from_user(const struct iovec __user *uvec,
1728         unsigned long nr_segs, unsigned long fast_segs,
1729         struct iovec *fast_iov, bool compat)
1730 {
1731     struct iovec *iov = fast_iov;
1732     int ret;
1733 
1734     /*
1735      * SuS says "The readv() function *may* fail if the iovcnt argument was
1736      * less than or equal to 0, or greater than {IOV_MAX}.  Linux has
1737      * traditionally returned zero for zero segments, so...
1738      */
1739     if (nr_segs == 0)
1740         return iov;
1741     if (nr_segs > UIO_MAXIOV)
1742         return ERR_PTR(-EINVAL);
1743     if (nr_segs > fast_segs) {
1744         iov = kmalloc_array(nr_segs, sizeof(struct iovec), GFP_KERNEL);
1745         if (!iov)
1746             return ERR_PTR(-ENOMEM);
1747     }
1748 
1749     if (compat)
1750         ret = copy_compat_iovec_from_user(iov, uvec, nr_segs);
1751     else
1752         ret = copy_iovec_from_user(iov, uvec, nr_segs);
1753     if (ret) {
1754         if (iov != fast_iov)
1755             kfree(iov);
1756         return ERR_PTR(ret);
1757     }
1758 
1759     return iov;
1760 }
1761 
1762 ssize_t __import_iovec(int type, const struct iovec __user *uvec,
1763          unsigned nr_segs, unsigned fast_segs, struct iovec **iovp,
1764          struct iov_iter *i, bool compat)
1765 {
1766     ssize_t total_len = 0;
1767     unsigned long seg;
1768     struct iovec *iov;
1769 
1770     iov = iovec_from_user(uvec, nr_segs, fast_segs, *iovp, compat);
1771     if (IS_ERR(iov)) {
1772         *iovp = NULL;
1773         return PTR_ERR(iov);
1774     }
1775 
1776     /*
1777      * According to the Single Unix Specification we should return EINVAL if
1778      * an element length is < 0 when cast to ssize_t or if the total length
1779      * would overflow the ssize_t return value of the system call.
1780      *
1781      * Linux caps all read/write calls to MAX_RW_COUNT, and avoids the
1782      * overflow case.
1783      */
1784     for (seg = 0; seg < nr_segs; seg++) {
1785         ssize_t len = (ssize_t)iov[seg].iov_len;
1786 
1787         if (!access_ok(iov[seg].iov_base, len)) {
1788             if (iov != *iovp)
1789                 kfree(iov);
1790             *iovp = NULL;
1791             return -EFAULT;
1792         }
1793 
1794         if (len > MAX_RW_COUNT - total_len) {
1795             len = MAX_RW_COUNT - total_len;
1796             iov[seg].iov_len = len;
1797         }
1798         total_len += len;
1799     }
1800 
1801     iov_iter_init(i, type, iov, nr_segs, total_len);
1802     if (iov == *iovp)
1803         *iovp = NULL;
1804     else
1805         *iovp = iov;
1806     return total_len;
1807 }
1808 
1809 /**
1810  * import_iovec() - Copy an array of &struct iovec from userspace
1811  *     into the kernel, check that it is valid, and initialize a new
1812  *     &struct iov_iter iterator to access it.
1813  *
1814  * @type: One of %READ or %WRITE.
1815  * @uvec: Pointer to the userspace array.
1816  * @nr_segs: Number of elements in userspace array.
1817  * @fast_segs: Number of elements in @iov.
1818  * @iovp: (input and output parameter) Pointer to pointer to (usually small
1819  *     on-stack) kernel array.
1820  * @i: Pointer to iterator that will be initialized on success.
1821  *
1822  * If the array pointed to by *@iov is large enough to hold all @nr_segs,
1823  * then this function places %NULL in *@iov on return. Otherwise, a new
1824  * array will be allocated and the result placed in *@iov. This means that
1825  * the caller may call kfree() on *@iov regardless of whether the small
1826  * on-stack array was used or not (and regardless of whether this function
1827  * returns an error or not).
1828  *
1829  * Return: Negative error code on error, bytes imported on success
1830  */
1831 ssize_t import_iovec(int type, const struct iovec __user *uvec,
1832          unsigned nr_segs, unsigned fast_segs,
1833          struct iovec **iovp, struct iov_iter *i)
1834 {
1835     return __import_iovec(type, uvec, nr_segs, fast_segs, iovp, i,
1836                   in_compat_syscall());
1837 }
1838 EXPORT_SYMBOL(import_iovec);
1839 
1840 int import_single_range(int rw, void __user *buf, size_t len,
1841          struct iovec *iov, struct iov_iter *i)
1842 {
1843     if (len > MAX_RW_COUNT)
1844         len = MAX_RW_COUNT;
1845     if (unlikely(!access_ok(buf, len)))
1846         return -EFAULT;
1847 
1848     iov->iov_base = buf;
1849     iov->iov_len = len;
1850     iov_iter_init(i, rw, iov, 1, len);
1851     return 0;
1852 }
1853 EXPORT_SYMBOL(import_single_range);
1854 
1855 /**
1856  * iov_iter_restore() - Restore a &struct iov_iter to the same state as when
1857  *     iov_iter_save_state() was called.
1858  *
1859  * @i: &struct iov_iter to restore
1860  * @state: state to restore from
1861  *
1862  * Used after iov_iter_save_state() to bring restore @i, if operations may
1863  * have advanced it.
1864  *
1865  * Note: only works on ITER_IOVEC, ITER_BVEC, and ITER_KVEC
1866  */
1867 void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state)
1868 {
1869     if (WARN_ON_ONCE(!iov_iter_is_bvec(i) && !iter_is_iovec(i)) &&
1870              !iov_iter_is_kvec(i) && !iter_is_ubuf(i))
1871         return;
1872     i->iov_offset = state->iov_offset;
1873     i->count = state->count;
1874     if (iter_is_ubuf(i))
1875         return;
1876     /*
1877      * For the *vec iters, nr_segs + iov is constant - if we increment
1878      * the vec, then we also decrement the nr_segs count. Hence we don't
1879      * need to track both of these, just one is enough and we can deduct
1880      * the other from that. ITER_KVEC and ITER_IOVEC are the same struct
1881      * size, so we can just increment the iov pointer as they are unionzed.
1882      * ITER_BVEC _may_ be the same size on some archs, but on others it is
1883      * not. Be safe and handle it separately.
1884      */
1885     BUILD_BUG_ON(sizeof(struct iovec) != sizeof(struct kvec));
1886     if (iov_iter_is_bvec(i))
1887         i->bvec -= state->nr_segs - i->nr_segs;
1888     else
1889         i->iov -= state->nr_segs - i->nr_segs;
1890     i->nr_segs = state->nr_segs;
1891 }
[ Source navigation ] [ Diff markup ] [ Identifier search ] [ general search ]

This page was automatically generated by the 2.1.0 LXR engine.

The LXR team
Valid CSS 2.1! Valid HTML 4.01!