the-tree/fs/binfmt_aout.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  *  linux/fs/binfmt_aout.c
0004  *
0005  *  Copyright (C) 1991, 1992, 1996  Linus Torvalds
0006  */
0007
0008 #include <linux/module.h>
0009
0010 #include <linux/time.h>
0011 #include <linux/kernel.h>
0012 #include <linux/mm.h>
0013 #include <linux/mman.h>
0014 #include <linux/a.out.h>
0015 #include <linux/errno.h>
0016 #include <linux/signal.h>
0017 #include <linux/string.h>
0018 #include <linux/fs.h>
0019 #include <linux/file.h>
0020 #include <linux/stat.h>
0021 #include <linux/fcntl.h>
0022 #include <linux/ptrace.h>
0023 #include <linux/user.h>
0024 #include <linux/binfmts.h>
0025 #include <linux/personality.h>
0026 #include <linux/init.h>
0027 #include <linux/coredump.h>
0028 #include <linux/slab.h>
0029 #include <linux/sched/task_stack.h>
0030
0031 #include <linux/uaccess.h>
0032 #include <asm/cacheflush.h>
0033
0034 static int load_aout_binary(struct linux_binprm *);
0035 static int load_aout_library(struct file*);
0036
0037 static struct linux_binfmt aout_format = {
0038     .module     = THIS_MODULE,
0039     .load_binary    = load_aout_binary,
0040     .load_shlib = load_aout_library,
0041 };
0042
0043 #define BAD_ADDR(x) ((unsigned long)(x) >= TASK_SIZE)
0044
0045 static int set_brk(unsigned long start, unsigned long end)
0046 {
0047     start = PAGE_ALIGN(start);
0048     end = PAGE_ALIGN(end);
0049     if (end > start)
0050         return vm_brk(start, end - start);
0051     return 0;
0052 }
0053
0054 /*
0055  * create_aout_tables() parses the env- and arg-strings in new user
0056  * memory and creates the pointer tables from them, and puts their
0057  * addresses on the "stack", returning the new stack pointer value.
0058  */
0059 static unsigned long __user *create_aout_tables(char __user *p, struct linux_binprm * bprm)
0060 {
0061     char __user * __user *argv;
0062     char __user * __user *envp;
0063     unsigned long __user *sp;
0064     int argc = bprm->argc;
0065     int envc = bprm->envc;
0066
0067     sp = (void __user *)((-(unsigned long)sizeof(char *)) & (unsigned long) p);
0068 #ifdef __alpha__
0069 /* whee.. test-programs are so much fun. */
0070     put_user(0, --sp);
0071     put_user(0, --sp);
0072     if (bprm->loader) {
0073         put_user(0, --sp);
0074         put_user(1003, --sp);
0075         put_user(bprm->loader, --sp);
0076         put_user(1002, --sp);
0077     }
0078     put_user(bprm->exec, --sp);
0079     put_user(1001, --sp);
0080 #endif
0081     sp -= envc+1;
0082     envp = (char __user * __user *) sp;
0083     sp -= argc+1;
0084     argv = (char __user * __user *) sp;
0085 #ifndef __alpha__
0086     put_user((unsigned long) envp,--sp);
0087     put_user((unsigned long) argv,--sp);
0088 #endif
0089     put_user(argc,--sp);
0090     current->mm->arg_start = (unsigned long) p;
0091     while (argc-->0) {
0092         char c;
0093         put_user(p,argv++);
0094         do {
0095             get_user(c,p++);
0096         } while (c);
0097     }
0098     put_user(NULL,argv);
0099     current->mm->arg_end = current->mm->env_start = (unsigned long) p;
0100     while (envc-->0) {
0101         char c;
0102         put_user(p,envp++);
0103         do {
0104             get_user(c,p++);
0105         } while (c);
0106     }
0107     put_user(NULL,envp);
0108     current->mm->env_end = (unsigned long) p;
0109     return sp;
0110 }
0111
0112 /*
0113  * These are the functions used to load a.out style executables and shared
0114  * libraries.  There is no binary dependent code anywhere else.
0115  */
0116
0117 static int load_aout_binary(struct linux_binprm * bprm)
0118 {
0119     struct pt_regs *regs = current_pt_regs();
0120     struct exec ex;
0121     unsigned long error;
0122     unsigned long fd_offset;
0123     unsigned long rlim;
0124     int retval;
0125
0126     ex = *((struct exec *) bprm->buf);      /* exec-header */
0127     if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != OMAGIC &&
0128          N_MAGIC(ex) != QMAGIC && N_MAGIC(ex) != NMAGIC) ||
0129         N_TRSIZE(ex) || N_DRSIZE(ex) ||
0130         i_size_read(file_inode(bprm->file)) < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
0131         return -ENOEXEC;
0132     }
0133
0134     /*
0135      * Requires a mmap handler. This prevents people from using a.out
0136      * as part of an exploit attack against /proc-related vulnerabilities.
0137      */
0138     if (!bprm->file->f_op->mmap)
0139         return -ENOEXEC;
0140
0141     fd_offset = N_TXTOFF(ex);
0142
0143     /* Check initial limits. This avoids letting people circumvent
0144      * size limits imposed on them by creating programs with large
0145      * arrays in the data or bss.
0146      */
0147     rlim = rlimit(RLIMIT_DATA);
0148     if (rlim >= RLIM_INFINITY)
0149         rlim = ~0;
0150     if (ex.a_data + ex.a_bss > rlim)
0151         return -ENOMEM;
0152
0153     /* Flush all traces of the currently running executable */
0154     retval = begin_new_exec(bprm);
0155     if (retval)
0156         return retval;
0157
0158     /* OK, This is the point of no return */
0159 #ifdef __alpha__
0160     SET_AOUT_PERSONALITY(bprm, ex);
0161 #else
0162     set_personality(PER_LINUX);
0163 #endif
0164     setup_new_exec(bprm);
0165
0166     current->mm->end_code = ex.a_text +
0167         (current->mm->start_code = N_TXTADDR(ex));
0168     current->mm->end_data = ex.a_data +
0169         (current->mm->start_data = N_DATADDR(ex));
0170     current->mm->brk = ex.a_bss +
0171         (current->mm->start_brk = N_BSSADDR(ex));
0172
0173     retval = setup_arg_pages(bprm, STACK_TOP, EXSTACK_DEFAULT);
0174     if (retval < 0)
0175         return retval;
0176
0177
0178     if (N_MAGIC(ex) == OMAGIC) {
0179         unsigned long text_addr, map_size;
0180         loff_t pos;
0181
0182         text_addr = N_TXTADDR(ex);
0183
0184 #ifdef __alpha__
0185         pos = fd_offset;
0186         map_size = ex.a_text+ex.a_data + PAGE_SIZE - 1;
0187 #else
0188         pos = 32;
0189         map_size = ex.a_text+ex.a_data;
0190 #endif
0191         error = vm_brk(text_addr & PAGE_MASK, map_size);
0192         if (error)
0193             return error;
0194
0195         error = read_code(bprm->file, text_addr, pos,
0196                   ex.a_text+ex.a_data);
0197         if ((signed long)error < 0)
0198             return error;
0199     } else {
0200         if ((ex.a_text & 0xfff || ex.a_data & 0xfff) &&
0201             (N_MAGIC(ex) != NMAGIC) && printk_ratelimit())
0202         {
0203             printk(KERN_NOTICE "executable not page aligned\n");
0204         }
0205
0206         if ((fd_offset & ~PAGE_MASK) != 0 && printk_ratelimit())
0207         {
0208             printk(KERN_WARNING
0209                    "fd_offset is not page aligned. Please convert program: %pD\n",
0210                    bprm->file);
0211         }
0212
0213         if (!bprm->file->f_op->mmap||((fd_offset & ~PAGE_MASK) != 0)) {
0214             error = vm_brk(N_TXTADDR(ex), ex.a_text+ex.a_data);
0215             if (error)
0216                 return error;
0217
0218             read_code(bprm->file, N_TXTADDR(ex), fd_offset,
0219                   ex.a_text + ex.a_data);
0220             goto beyond_if;
0221         }
0222
0223         error = vm_mmap(bprm->file, N_TXTADDR(ex), ex.a_text,
0224             PROT_READ | PROT_EXEC, MAP_FIXED | MAP_PRIVATE,
0225             fd_offset);
0226
0227         if (error != N_TXTADDR(ex))
0228             return error;
0229
0230         error = vm_mmap(bprm->file, N_DATADDR(ex), ex.a_data,
0231                 PROT_READ | PROT_WRITE | PROT_EXEC,
0232                 MAP_FIXED | MAP_PRIVATE,
0233                 fd_offset + ex.a_text);
0234         if (error != N_DATADDR(ex))
0235             return error;
0236     }
0237 beyond_if:
0238     set_binfmt(&aout_format);
0239
0240     retval = set_brk(current->mm->start_brk, current->mm->brk);
0241     if (retval < 0)
0242         return retval;
0243
0244     current->mm->start_stack =
0245         (unsigned long) create_aout_tables((char __user *) bprm->p, bprm);
0246 #ifdef __alpha__
0247     regs->gp = ex.a_gpvalue;
0248 #endif
0249     finalize_exec(bprm);
0250     start_thread(regs, ex.a_entry, current->mm->start_stack);
0251     return 0;
0252 }
0253
0254 static int load_aout_library(struct file *file)
0255 {
0256     struct inode * inode;
0257     unsigned long bss, start_addr, len;
0258     unsigned long error;
0259     int retval;
0260     struct exec ex;
0261     loff_t pos = 0;
0262
0263     inode = file_inode(file);
0264
0265     retval = -ENOEXEC;
0266     error = kernel_read(file, &ex, sizeof(ex), &pos);
0267     if (error != sizeof(ex))
0268         goto out;
0269
0270     /* We come in here for the regular a.out style of shared libraries */
0271     if ((N_MAGIC(ex) != ZMAGIC && N_MAGIC(ex) != QMAGIC) || N_TRSIZE(ex) ||
0272         N_DRSIZE(ex) || ((ex.a_entry & 0xfff) && N_MAGIC(ex) == ZMAGIC) ||
0273         i_size_read(inode) < ex.a_text+ex.a_data+N_SYMSIZE(ex)+N_TXTOFF(ex)) {
0274         goto out;
0275     }
0276
0277     /*
0278      * Requires a mmap handler. This prevents people from using a.out
0279      * as part of an exploit attack against /proc-related vulnerabilities.
0280      */
0281     if (!file->f_op->mmap)
0282         goto out;
0283
0284     if (N_FLAGS(ex))
0285         goto out;
0286
0287     /* For  QMAGIC, the starting address is 0x20 into the page.  We mask
0288        this off to get the starting address for the page */
0289
0290     start_addr =  ex.a_entry & 0xfffff000;
0291
0292     if ((N_TXTOFF(ex) & ~PAGE_MASK) != 0) {
0293         if (printk_ratelimit())
0294         {
0295             printk(KERN_WARNING
0296                    "N_TXTOFF is not page aligned. Please convert library: %pD\n",
0297                    file);
0298         }
0299         retval = vm_brk(start_addr, ex.a_text + ex.a_data + ex.a_bss);
0300         if (retval)
0301             goto out;
0302
0303         read_code(file, start_addr, N_TXTOFF(ex),
0304               ex.a_text + ex.a_data);
0305         retval = 0;
0306         goto out;
0307     }
0308     /* Now use mmap to map the library into memory. */
0309     error = vm_mmap(file, start_addr, ex.a_text + ex.a_data,
0310             PROT_READ | PROT_WRITE | PROT_EXEC,
0311             MAP_FIXED | MAP_PRIVATE,
0312             N_TXTOFF(ex));
0313     retval = error;
0314     if (error != start_addr)
0315         goto out;
0316
0317     len = PAGE_ALIGN(ex.a_text + ex.a_data);
0318     bss = ex.a_text + ex.a_data + ex.a_bss;
0319     if (bss > len) {
0320         retval = vm_brk(start_addr + len, bss - len);
0321         if (retval)
0322             goto out;
0323     }
0324     retval = 0;
0325 out:
0326     return retval;
0327 }
0328
0329 static int __init init_aout_binfmt(void)
0330 {
0331     register_binfmt(&aout_format);
0332     return 0;
0333 }
0334
0335 static void __exit exit_aout_binfmt(void)
0336 {
0337     unregister_binfmt(&aout_format);
0338 }
0339
0340 core_initcall(init_aout_binfmt);
0341 module_exit(exit_aout_binfmt);
0342 MODULE_LICENSE("GPL");