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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
 /*
  * Copyright (C) 2017-2022 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
  * Copyright Matt Mackall <mpm@selenic.com>, 2003, 2004, 2005
  * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998, 1999. All rights reserved.
  *
  * This driver produces cryptographically secure pseudorandom data. It is divided
  * into roughly six sections, each with a section header:
  *
  *   - Initialization and readiness waiting.
  *   - Fast key erasure RNG, the "crng".
  *   - Entropy accumulation and extraction routines.
  *   - Entropy collection routines.
  *   - Userspace reader/writer interfaces.
  *   - Sysctl interface.
  *
  * The high level overview is that there is one input pool, into which
  * various pieces of data are hashed. Prior to initialization, some of that
  * data is then "credited" as having a certain number of bits of entropy.
  * When enough bits of entropy are available, the hash is finalized and
  * handed as a key to a stream cipher that expands it indefinitely for
  * various consumers. This key is periodically refreshed as the various
  * entropy collectors, described below, add data to the input pool.
  */
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
 #include <linux/utsname.h>
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/major.h>
 #include <linux/string.h>
 #include <linux/fcntl.h>
 #include <linux/slab.h>
 #include <linux/random.h>
 #include <linux/poll.h>
 #include <linux/init.h>
 #include <linux/fs.h>
 #include <linux/blkdev.h>
 #include <linux/interrupt.h>
 #include <linux/mm.h>
 #include <linux/nodemask.h>
 #include <linux/spinlock.h>
 #include <linux/kthread.h>
 #include <linux/percpu.h>
 #include <linux/ptrace.h>
 #include <linux/workqueue.h>
 #include <linux/irq.h>
 #include <linux/ratelimit.h>
 #include <linux/syscalls.h>
 #include <linux/completion.h>
 #include <linux/uuid.h>
 #include <linux/uaccess.h>
 #include <linux/suspend.h>
 #include <linux/siphash.h>
 #include <crypto/chacha.h>
 #include <crypto/blake2s.h>
 #include <asm/processor.h>
 #include <asm/irq.h>
 #include <asm/irq_regs.h>
 #include <asm/io.h>
 
 /*********************************************************************
  *
  * Initialization and readiness waiting.
  *
  * Much of the RNG infrastructure is devoted to various dependencies
  * being able to wait until the RNG has collected enough entropy and
  * is ready for safe consumption.
  *
  *********************************************************************/
 
 /*
  * crng_init is protected by base_crng->lock, and only increases
  * its value (from empty->early->ready).
  */
 static enum {
     CRNG_EMPTY = 0, /* Little to no entropy collected */
     CRNG_EARLY = 1, /* At least POOL_EARLY_BITS collected */
     CRNG_READY = 2  /* Fully initialized with POOL_READY_BITS collected */
 } crng_init __read_mostly = CRNG_EMPTY;
 static DEFINE_STATIC_KEY_FALSE(crng_is_ready);
 #define crng_ready() (static_branch_likely(&crng_is_ready) || crng_init >= CRNG_READY)
 /* Various types of waiters for crng_init->CRNG_READY transition. */
 static DECLARE_WAIT_QUEUE_HEAD(crng_init_wait);
 static struct fasync_struct *fasync;
 
 /* Control how we warn userspace. */
 static struct ratelimit_state urandom_warning =
     RATELIMIT_STATE_INIT_FLAGS("urandom_warning", HZ, 3, RATELIMIT_MSG_ON_RELEASE);
 static int ratelimit_disable __read_mostly =
     IS_ENABLED(CONFIG_WARN_ALL_UNSEEDED_RANDOM);
 module_param_named(ratelimit_disable, ratelimit_disable, int, 0644);
 MODULE_PARM_DESC(ratelimit_disable, "Disable random ratelimit suppression");
 
 /*
  * Returns whether or not the input pool has been seeded and thus guaranteed
  * to supply cryptographically secure random numbers. This applies to: the
  * /dev/urandom device, the get_random_bytes function, and the get_random_{u32,
  * ,u64,int,long} family of functions.
  *
  * Returns: true if the input pool has been seeded.
  *          false if the input pool has not been seeded.
  */
 bool rng_is_initialized(void)
 {
     return crng_ready();
 }
 EXPORT_SYMBOL(rng_is_initialized);
 
 static void __cold crng_set_ready(struct work_struct *work)
 {
     static_branch_enable(&crng_is_ready);
 }
 
 /* Used by wait_for_random_bytes(), and considered an entropy collector, below. */
 static void try_to_generate_entropy(void);
 
 /*
  * Wait for the input pool to be seeded and thus guaranteed to supply
  * cryptographically secure random numbers. This applies to: the /dev/urandom
  * device, the get_random_bytes function, and the get_random_{u32,u64,int,long}
  * family of functions. Using any of these functions without first calling
  * this function forfeits the guarantee of security.
  *
  * Returns: 0 if the input pool has been seeded.
  *          -ERESTARTSYS if the function was interrupted by a signal.
  */
 int wait_for_random_bytes(void)
 {
     while (!crng_ready()) {
         int ret;
 
         try_to_generate_entropy();
         ret = wait_event_interruptible_timeout(crng_init_wait, crng_ready(), HZ);
         if (ret)
             return ret > 0 ? 0 : ret;
     }
     return 0;
 }
 EXPORT_SYMBOL(wait_for_random_bytes);
 
 #define warn_unseeded_randomness() \
     if (IS_ENABLED(CONFIG_WARN_ALL_UNSEEDED_RANDOM) && !crng_ready()) \
         printk_deferred(KERN_NOTICE "random: %s called from %pS with crng_init=%d\n", \
                 __func__, (void *)_RET_IP_, crng_init)
 
 
 /*********************************************************************
  *
  * Fast key erasure RNG, the "crng".
  *
  * These functions expand entropy from the entropy extractor into
  * long streams for external consumption using the "fast key erasure"
  * RNG described at <https://blog.cr.yp.to/20170723-random.html>.
  *
  * There are a few exported interfaces for use by other drivers:
  *
  *  void get_random_bytes(void *buf, size_t len)
  *  u32 get_random_u32()
  *  u64 get_random_u64()
  *  unsigned int get_random_int()
  *  unsigned long get_random_long()
  *
  * These interfaces will return the requested number of random bytes
  * into the given buffer or as a return value. This is equivalent to
  * a read from /dev/urandom. The u32, u64, int, and long family of
  * functions may be higher performance for one-off random integers,
  * because they do a bit of buffering and do not invoke reseeding
  * until the buffer is emptied.
  *
  *********************************************************************/
 
 enum {
     CRNG_RESEED_START_INTERVAL = HZ,
     CRNG_RESEED_INTERVAL = 60 * HZ
 };
 
 static struct {
     u8 key[CHACHA_KEY_SIZE] __aligned(__alignof__(long));
     unsigned long birth;
     unsigned long generation;
     spinlock_t lock;
 } base_crng = {
     .lock = __SPIN_LOCK_UNLOCKED(base_crng.lock)
 };
 
 struct crng {
     u8 key[CHACHA_KEY_SIZE];
     unsigned long generation;
     local_lock_t lock;
 };
 
 static DEFINE_PER_CPU(struct crng, crngs) = {
     .generation = ULONG_MAX,
     .lock = INIT_LOCAL_LOCK(crngs.lock),
 };
 
 /* Used by crng_reseed() and crng_make_state() to extract a new seed from the input pool. */
 static void extract_entropy(void *buf, size_t len);
 
 /* This extracts a new crng key from the input pool. */
 static void crng_reseed(void)
 {
     unsigned long flags;
     unsigned long next_gen;
     u8 key[CHACHA_KEY_SIZE];
 
     extract_entropy(key, sizeof(key));
 
     /*
      * We copy the new key into the base_crng, overwriting the old one,
      * and update the generation counter. We avoid hitting ULONG_MAX,
      * because the per-cpu crngs are initialized to ULONG_MAX, so this
      * forces new CPUs that come online to always initialize.
      */
     spin_lock_irqsave(&base_crng.lock, flags);
     memcpy(base_crng.key, key, sizeof(base_crng.key));
     next_gen = base_crng.generation + 1;
     if (next_gen == ULONG_MAX)
         ++next_gen;
     WRITE_ONCE(base_crng.generation, next_gen);
     WRITE_ONCE(base_crng.birth, jiffies);
     if (!static_branch_likely(&crng_is_ready))
         crng_init = CRNG_READY;
     spin_unlock_irqrestore(&base_crng.lock, flags);
     memzero_explicit(key, sizeof(key));
 }
 
 /*
  * This generates a ChaCha block using the provided key, and then
  * immediately overwrites that key with half the block. It returns
  * the resultant ChaCha state to the user, along with the second
  * half of the block containing 32 bytes of random data that may
  * be used; random_data_len may not be greater than 32.
  *
  * The returned ChaCha state contains within it a copy of the old
  * key value, at index 4, so the state should always be zeroed out
  * immediately after using in order to maintain forward secrecy.
  * If the state cannot be erased in a timely manner, then it is
  * safer to set the random_data parameter to &chacha_state[4] so
  * that this function overwrites it before returning.
  */
 static void crng_fast_key_erasure(u8 key[CHACHA_KEY_SIZE],
                   u32 chacha_state[CHACHA_STATE_WORDS],
                   u8 *random_data, size_t random_data_len)
 {
     u8 first_block[CHACHA_BLOCK_SIZE];
 
     BUG_ON(random_data_len > 32);
 
     chacha_init_consts(chacha_state);
     memcpy(&chacha_state[4], key, CHACHA_KEY_SIZE);
     memset(&chacha_state[12], 0, sizeof(u32) * 4);
     chacha20_block(chacha_state, first_block);
 
     memcpy(key, first_block, CHACHA_KEY_SIZE);
     memcpy(random_data, first_block + CHACHA_KEY_SIZE, random_data_len);
     memzero_explicit(first_block, sizeof(first_block));
 }
 
 /*
  * Return whether the crng seed is considered to be sufficiently old
  * that a reseeding is needed. This happens if the last reseeding
  * was CRNG_RESEED_INTERVAL ago, or during early boot, at an interval
  * proportional to the uptime.
  */
 static bool crng_has_old_seed(void)
 {
     static bool early_boot = true;
     unsigned long interval = CRNG_RESEED_INTERVAL;
 
     if (unlikely(READ_ONCE(early_boot))) {
         time64_t uptime = ktime_get_seconds();
         if (uptime >= CRNG_RESEED_INTERVAL / HZ * 2)
             WRITE_ONCE(early_boot, false);
         else
             interval = max_t(unsigned int, CRNG_RESEED_START_INTERVAL,
                      (unsigned int)uptime / 2 * HZ);
     }
     return time_is_before_jiffies(READ_ONCE(base_crng.birth) + interval);
 }
 
 /*
  * This function returns a ChaCha state that you may use for generating
  * random data. It also returns up to 32 bytes on its own of random data
  * that may be used; random_data_len may not be greater than 32.
  */
 static void crng_make_state(u32 chacha_state[CHACHA_STATE_WORDS],
                 u8 *random_data, size_t random_data_len)
 {
     unsigned long flags;
     struct crng *crng;
 
     BUG_ON(random_data_len > 32);
 
     /*
      * For the fast path, we check whether we're ready, unlocked first, and
      * then re-check once locked later. In the case where we're really not
      * ready, we do fast key erasure with the base_crng directly, extracting
      * when crng_init is CRNG_EMPTY.
      */
     if (!crng_ready()) {
         bool ready;
 
         spin_lock_irqsave(&base_crng.lock, flags);
         ready = crng_ready();
         if (!ready) {
             if (crng_init == CRNG_EMPTY)
                 extract_entropy(base_crng.key, sizeof(base_crng.key));
             crng_fast_key_erasure(base_crng.key, chacha_state,
                           random_data, random_data_len);
         }
         spin_unlock_irqrestore(&base_crng.lock, flags);
         if (!ready)
             return;
     }
 
     /*
      * If the base_crng is old enough, we reseed, which in turn bumps the
      * generation counter that we check below.
      */
     if (unlikely(crng_has_old_seed()))
         crng_reseed();
 
     local_lock_irqsave(&crngs.lock, flags);
     crng = raw_cpu_ptr(&crngs);
 
     /*
      * If our per-cpu crng is older than the base_crng, then it means
      * somebody reseeded the base_crng. In that case, we do fast key
      * erasure on the base_crng, and use its output as the new key
      * for our per-cpu crng. This brings us up to date with base_crng.
      */
     if (unlikely(crng->generation != READ_ONCE(base_crng.generation))) {
         spin_lock(&base_crng.lock);
         crng_fast_key_erasure(base_crng.key, chacha_state,
                       crng->key, sizeof(crng->key));
         crng->generation = base_crng.generation;
         spin_unlock(&base_crng.lock);
     }
 
     /*
      * Finally, when we've made it this far, our per-cpu crng has an up
      * to date key, and we can do fast key erasure with it to produce
      * some random data and a ChaCha state for the caller. All other
      * branches of this function are "unlikely", so most of the time we
      * should wind up here immediately.
      */
     crng_fast_key_erasure(crng->key, chacha_state, random_data, random_data_len);
     local_unlock_irqrestore(&crngs.lock, flags);
 }
 
 static void _get_random_bytes(void *buf, size_t len)
 {
     u32 chacha_state[CHACHA_STATE_WORDS];
     u8 tmp[CHACHA_BLOCK_SIZE];
     size_t first_block_len;
 
     if (!len)
         return;
 
     first_block_len = min_t(size_t, 32, len);
     crng_make_state(chacha_state, buf, first_block_len);
     len -= first_block_len;
     buf += first_block_len;
 
     while (len) {
         if (len < CHACHA_BLOCK_SIZE) {
             chacha20_block(chacha_state, tmp);
             memcpy(buf, tmp, len);
             memzero_explicit(tmp, sizeof(tmp));
             break;
         }
 
         chacha20_block(chacha_state, buf);
         if (unlikely(chacha_state[12] == 0))
             ++chacha_state[13];
         len -= CHACHA_BLOCK_SIZE;
         buf += CHACHA_BLOCK_SIZE;
     }
 
     memzero_explicit(chacha_state, sizeof(chacha_state));
 }
 
 /*
  * This function is the exported kernel interface.  It returns some
  * number of good random numbers, suitable for key generation, seeding
  * TCP sequence numbers, etc. In order to ensure that the randomness
  * by this function is okay, the function wait_for_random_bytes()
  * should be called and return 0 at least once at any point prior.
  */
 void get_random_bytes(void *buf, size_t len)
 {
     warn_unseeded_randomness();
     _get_random_bytes(buf, len);
 }
 EXPORT_SYMBOL(get_random_bytes);
 
 static ssize_t get_random_bytes_user(struct iov_iter *iter)
 {
     u32 chacha_state[CHACHA_STATE_WORDS];
     u8 block[CHACHA_BLOCK_SIZE];
     size_t ret = 0, copied;
 
     if (unlikely(!iov_iter_count(iter)))
         return 0;
 
     /*
      * Immediately overwrite the ChaCha key at index 4 with random
      * bytes, in case userspace causes copy_to_iter() below to sleep
      * forever, so that we still retain forward secrecy in that case.
      */
     crng_make_state(chacha_state, (u8 *)&chacha_state[4], CHACHA_KEY_SIZE);
     /*
      * However, if we're doing a read of len <= 32, we don't need to
      * use chacha_state after, so we can simply return those bytes to
      * the user directly.
      */
     if (iov_iter_count(iter) <= CHACHA_KEY_SIZE) {
         ret = copy_to_iter(&chacha_state[4], CHACHA_KEY_SIZE, iter);
         goto out_zero_chacha;
     }
 
     for (;;) {
         chacha20_block(chacha_state, block);
         if (unlikely(chacha_state[12] == 0))
             ++chacha_state[13];
 
         copied = copy_to_iter(block, sizeof(block), iter);
         ret += copied;
         if (!iov_iter_count(iter) || copied != sizeof(block))
             break;
 
         BUILD_BUG_ON(PAGE_SIZE % sizeof(block) != 0);
         if (ret % PAGE_SIZE == 0) {
             if (signal_pending(current))
                 break;
             cond_resched();
         }
     }
 
     memzero_explicit(block, sizeof(block));
 out_zero_chacha:
     memzero_explicit(chacha_state, sizeof(chacha_state));
     return ret ? ret : -EFAULT;
 }
 
 /*
  * Batched entropy returns random integers. The quality of the random
  * number is good as /dev/urandom. In order to ensure that the randomness
  * provided by this function is okay, the function wait_for_random_bytes()
  * should be called and return 0 at least once at any point prior.
  */
 
 #define DEFINE_BATCHED_ENTROPY(type)                        \
 struct batch_ ##type {                              \
     /*                                  \
      * We make this 1.5x a ChaCha block, so that we get the         \
      * remaining 32 bytes from fast key erasure, plus one full      \
      * block from the detached ChaCha state. We can increase        \
      * the size of this later if needed so long as we keep the      \
      * formula of (integer_blocks + 0.5) * CHACHA_BLOCK_SIZE.       \
      */                                 \
     type entropy[CHACHA_BLOCK_SIZE * 3 / (2 * sizeof(type))];       \
     local_lock_t lock;                          \
     unsigned long generation;                       \
     unsigned int position;                          \
 };                                      \
                                         \
 static DEFINE_PER_CPU(struct batch_ ##type, batched_entropy_ ##type) = {    \
     .lock = INIT_LOCAL_LOCK(batched_entropy_ ##type.lock),          \
     .position = UINT_MAX                            \
 };                                      \
                                         \
 type get_random_ ##type(void)                           \
 {                                       \
     type ret;                               \
     unsigned long flags;                            \
     struct batch_ ##type *batch;                        \
     unsigned long next_gen;                         \
                                         \
     warn_unseeded_randomness();                     \
                                         \
     if  (!crng_ready()) {                           \
         _get_random_bytes(&ret, sizeof(ret));               \
         return ret;                         \
     }                                   \
                                         \
     local_lock_irqsave(&batched_entropy_ ##type.lock, flags);       \
     batch = raw_cpu_ptr(&batched_entropy_##type);               \
                                         \
     next_gen = READ_ONCE(base_crng.generation);             \
     if (batch->position >= ARRAY_SIZE(batch->entropy) ||            \
         next_gen != batch->generation) {                    \
         _get_random_bytes(batch->entropy, sizeof(batch->entropy));  \
         batch->position = 0;                        \
         batch->generation = next_gen;                   \
     }                                   \
                                         \
     ret = batch->entropy[batch->position];                  \
     batch->entropy[batch->position] = 0;                    \
     ++batch->position;                          \
     local_unlock_irqrestore(&batched_entropy_ ##type.lock, flags);      \
     return ret;                             \
 }                                       \
 EXPORT_SYMBOL(get_random_ ##type);
 
 DEFINE_BATCHED_ENTROPY(u64)
 DEFINE_BATCHED_ENTROPY(u32)
 
 #ifdef CONFIG_SMP
 /*
  * This function is called when the CPU is coming up, with entry
  * CPUHP_RANDOM_PREPARE, which comes before CPUHP_WORKQUEUE_PREP.
  */
 int __cold random_prepare_cpu(unsigned int cpu)
 {
     /*
      * When the cpu comes back online, immediately invalidate both
      * the per-cpu crng and all batches, so that we serve fresh
      * randomness.
      */
     per_cpu_ptr(&crngs, cpu)->generation = ULONG_MAX;
     per_cpu_ptr(&batched_entropy_u32, cpu)->position = UINT_MAX;
     per_cpu_ptr(&batched_entropy_u64, cpu)->position = UINT_MAX;
     return 0;
 }
 #endif
 
 
 /**********************************************************************
  *
  * Entropy accumulation and extraction routines.
  *
  * Callers may add entropy via:
  *
  *     static void mix_pool_bytes(const void *buf, size_t len)
  *
  * After which, if added entropy should be credited:
  *
  *     static void credit_init_bits(size_t bits)
  *
  * Finally, extract entropy via:
  *
  *     static void extract_entropy(void *buf, size_t len)
  *
  **********************************************************************/
 
 enum {
     POOL_BITS = BLAKE2S_HASH_SIZE * 8,
     POOL_READY_BITS = POOL_BITS, /* When crng_init->CRNG_READY */
     POOL_EARLY_BITS = POOL_READY_BITS / 2 /* When crng_init->CRNG_EARLY */
 };
 
 static struct {
     struct blake2s_state hash;
     spinlock_t lock;
     unsigned int init_bits;
 } input_pool = {
     .hash.h = { BLAKE2S_IV0 ^ (0x01010000 | BLAKE2S_HASH_SIZE),
             BLAKE2S_IV1, BLAKE2S_IV2, BLAKE2S_IV3, BLAKE2S_IV4,
             BLAKE2S_IV5, BLAKE2S_IV6, BLAKE2S_IV7 },
     .hash.outlen = BLAKE2S_HASH_SIZE,
     .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock),
 };
 
 static void _mix_pool_bytes(const void *buf, size_t len)
 {
     blake2s_update(&input_pool.hash, buf, len);
 }
 
 /*
  * This function adds bytes into the input pool. It does not
  * update the initialization bit counter; the caller should call
  * credit_init_bits if this is appropriate.
  */
 static void mix_pool_bytes(const void *buf, size_t len)
 {
     unsigned long flags;
 
     spin_lock_irqsave(&input_pool.lock, flags);
     _mix_pool_bytes(buf, len);
     spin_unlock_irqrestore(&input_pool.lock, flags);
 }
 
 /*
  * This is an HKDF-like construction for using the hashed collected entropy
  * as a PRF key, that's then expanded block-by-block.
  */
 static void extract_entropy(void *buf, size_t len)
 {
     unsigned long flags;
     u8 seed[BLAKE2S_HASH_SIZE], next_key[BLAKE2S_HASH_SIZE];
     struct {
         unsigned long rdseed[32 / sizeof(long)];
         size_t counter;
     } block;
     size_t i, longs;
 
     for (i = 0; i < ARRAY_SIZE(block.rdseed);) {
         longs = arch_get_random_seed_longs(&block.rdseed[i], ARRAY_SIZE(block.rdseed) - i);
         if (longs) {
             i += longs;
             continue;
         }
         longs = arch_get_random_longs(&block.rdseed[i], ARRAY_SIZE(block.rdseed) - i);
         if (longs) {
             i += longs;
             continue;
         }
         block.rdseed[i++] = random_get_entropy();
     }
 
     spin_lock_irqsave(&input_pool.lock, flags);
 
     /* seed = HASHPRF(last_key, entropy_input) */
     blake2s_final(&input_pool.hash, seed);
 
     /* next_key = HASHPRF(seed, RDSEED || 0) */
     block.counter = 0;
     blake2s(next_key, (u8 *)&block, seed, sizeof(next_key), sizeof(block), sizeof(seed));
     blake2s_init_key(&input_pool.hash, BLAKE2S_HASH_SIZE, next_key, sizeof(next_key));
 
     spin_unlock_irqrestore(&input_pool.lock, flags);
     memzero_explicit(next_key, sizeof(next_key));
 
     while (len) {
         i = min_t(size_t, len, BLAKE2S_HASH_SIZE);
         /* output = HASHPRF(seed, RDSEED || ++counter) */
         ++block.counter;
         blake2s(buf, (u8 *)&block, seed, i, sizeof(block), sizeof(seed));
         len -= i;
         buf += i;
     }
 
     memzero_explicit(seed, sizeof(seed));
     memzero_explicit(&block, sizeof(block));
 }
 
 #define credit_init_bits(bits) if (!crng_ready()) _credit_init_bits(bits)
 
 static void __cold _credit_init_bits(size_t bits)
 {
     static struct execute_work set_ready;
     unsigned int new, orig, add;
     unsigned long flags;
 
     if (!bits)
         return;
 
     add = min_t(size_t, bits, POOL_BITS);
 
     orig = READ_ONCE(input_pool.init_bits);
     do {
         new = min_t(unsigned int, POOL_BITS, orig + add);
     } while (!try_cmpxchg(&input_pool.init_bits, &orig, new));
 
     if (orig < POOL_READY_BITS && new >= POOL_READY_BITS) {
         crng_reseed(); /* Sets crng_init to CRNG_READY under base_crng.lock. */
         if (static_key_initialized)
             execute_in_process_context(crng_set_ready, &set_ready);
         wake_up_interruptible(&crng_init_wait);
         kill_fasync(&fasync, SIGIO, POLL_IN);
         pr_notice("crng init done\n");
         if (urandom_warning.missed)
             pr_notice("%d urandom warning(s) missed due to ratelimiting\n",
                   urandom_warning.missed);
     } else if (orig < POOL_EARLY_BITS && new >= POOL_EARLY_BITS) {
         spin_lock_irqsave(&base_crng.lock, flags);
         /* Check if crng_init is CRNG_EMPTY, to avoid race with crng_reseed(). */
         if (crng_init == CRNG_EMPTY) {
             extract_entropy(base_crng.key, sizeof(base_crng.key));
             crng_init = CRNG_EARLY;
         }
         spin_unlock_irqrestore(&base_crng.lock, flags);
     }
 }
 
 
 /**********************************************************************
  *
  * Entropy collection routines.
  *
  * The following exported functions are used for pushing entropy into
  * the above entropy accumulation routines:
  *
  *  void add_device_randomness(const void *buf, size_t len);
  *  void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy);
  *  void add_bootloader_randomness(const void *buf, size_t len);
  *  void add_vmfork_randomness(const void *unique_vm_id, size_t len);
  *  void add_interrupt_randomness(int irq);
  *  void add_input_randomness(unsigned int type, unsigned int code, unsigned int value);
  *  void add_disk_randomness(struct gendisk *disk);
  *
  * add_device_randomness() adds data to the input pool that
  * is likely to differ between two devices (or possibly even per boot).
  * This would be things like MAC addresses or serial numbers, or the
  * read-out of the RTC. This does *not* credit any actual entropy to
  * the pool, but it initializes the pool to different values for devices
  * that might otherwise be identical and have very little entropy
  * available to them (particularly common in the embedded world).
  *
  * add_hwgenerator_randomness() is for true hardware RNGs, and will credit
  * entropy as specified by the caller. If the entropy pool is full it will
  * block until more entropy is needed.
  *
  * add_bootloader_randomness() is called by bootloader drivers, such as EFI
  * and device tree, and credits its input depending on whether or not the
  * configuration option CONFIG_RANDOM_TRUST_BOOTLOADER is set.
  *
  * add_vmfork_randomness() adds a unique (but not necessarily secret) ID
  * representing the current instance of a VM to the pool, without crediting,
  * and then force-reseeds the crng so that it takes effect immediately.
  *
  * add_interrupt_randomness() uses the interrupt timing as random
  * inputs to the entropy pool. Using the cycle counters and the irq source
  * as inputs, it feeds the input pool roughly once a second or after 64
  * interrupts, crediting 1 bit of entropy for whichever comes first.
  *
  * add_input_randomness() uses the input layer interrupt timing, as well
  * as the event type information from the hardware.
  *
  * add_disk_randomness() uses what amounts to the seek time of block
  * layer request events, on a per-disk_devt basis, as input to the
  * entropy pool. Note that high-speed solid state drives with very low
  * seek times do not make for good sources of entropy, as their seek
  * times are usually fairly consistent.
  *
  * The last two routines try to estimate how many bits of entropy
  * to credit. They do this by keeping track of the first and second
  * order deltas of the event timings.
  *
  **********************************************************************/
 
 static bool trust_cpu __initdata = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU);
 static bool trust_bootloader __initdata = IS_ENABLED(CONFIG_RANDOM_TRUST_BOOTLOADER);
 static int __init parse_trust_cpu(char *arg)
 {
     return kstrtobool(arg, &trust_cpu);
 }
 static int __init parse_trust_bootloader(char *arg)
 {
     return kstrtobool(arg, &trust_bootloader);
 }
 early_param("random.trust_cpu", parse_trust_cpu);
 early_param("random.trust_bootloader", parse_trust_bootloader);
 
 static int random_pm_notification(struct notifier_block *nb, unsigned long action, void *data)
 {
     unsigned long flags, entropy = random_get_entropy();
 
     /*
      * Encode a representation of how long the system has been suspended,
      * in a way that is distinct from prior system suspends.
      */
     ktime_t stamps[] = { ktime_get(), ktime_get_boottime(), ktime_get_real() };
 
     spin_lock_irqsave(&input_pool.lock, flags);
     _mix_pool_bytes(&action, sizeof(action));
     _mix_pool_bytes(stamps, sizeof(stamps));
     _mix_pool_bytes(&entropy, sizeof(entropy));
     spin_unlock_irqrestore(&input_pool.lock, flags);
 
     if (crng_ready() && (action == PM_RESTORE_PREPARE ||
         (action == PM_POST_SUSPEND && !IS_ENABLED(CONFIG_PM_AUTOSLEEP) &&
          !IS_ENABLED(CONFIG_PM_USERSPACE_AUTOSLEEP)))) {
         crng_reseed();
         pr_notice("crng reseeded on system resumption\n");
     }
     return 0;
 }
 
 static struct notifier_block pm_notifier = { .notifier_call = random_pm_notification };
 
 /*
  * The first collection of entropy occurs at system boot while interrupts
  * are still turned off. Here we push in latent entropy, RDSEED, a timestamp,
  * utsname(), and the command line. Depending on the above configuration knob,
  * RDSEED may be considered sufficient for initialization. Note that much
  * earlier setup may already have pushed entropy into the input pool by the
  * time we get here.
  */
 int __init random_init(const char *command_line)
 {
     ktime_t now = ktime_get_real();
     size_t i, longs, arch_bits;
     unsigned long entropy[BLAKE2S_BLOCK_SIZE / sizeof(long)];
 
 #if defined(LATENT_ENTROPY_PLUGIN)
     static const u8 compiletime_seed[BLAKE2S_BLOCK_SIZE] __initconst __latent_entropy;
     _mix_pool_bytes(compiletime_seed, sizeof(compiletime_seed));
 #endif
 
     for (i = 0, arch_bits = sizeof(entropy) * 8; i < ARRAY_SIZE(entropy);) {
         longs = arch_get_random_seed_longs(entropy, ARRAY_SIZE(entropy) - i);
         if (longs) {
             _mix_pool_bytes(entropy, sizeof(*entropy) * longs);
             i += longs;
             continue;
         }
         longs = arch_get_random_longs(entropy, ARRAY_SIZE(entropy) - i);
         if (longs) {
             _mix_pool_bytes(entropy, sizeof(*entropy) * longs);
             i += longs;
             continue;
         }
         entropy[0] = random_get_entropy();
         _mix_pool_bytes(entropy, sizeof(*entropy));
         arch_bits -= sizeof(*entropy) * 8;
         ++i;
     }
     _mix_pool_bytes(&now, sizeof(now));
     _mix_pool_bytes(utsname(), sizeof(*(utsname())));
     _mix_pool_bytes(command_line, strlen(command_line));
     add_latent_entropy();
 
     /*
      * If we were initialized by the bootloader before jump labels are
      * initialized, then we should enable the static branch here, where
      * it's guaranteed that jump labels have been initialized.
      */
     if (!static_branch_likely(&crng_is_ready) && crng_init >= CRNG_READY)
         crng_set_ready(NULL);
 
     if (crng_ready())
         crng_reseed();
     else if (trust_cpu)
         _credit_init_bits(arch_bits);
 
     WARN_ON(register_pm_notifier(&pm_notifier));
 
     WARN(!random_get_entropy(), "Missing cycle counter and fallback timer; RNG "
                     "entropy collection will consequently suffer.");
     return 0;
 }
 
 /*
  * Add device- or boot-specific data to the input pool to help
  * initialize it.
  *
  * None of this adds any entropy; it is meant to avoid the problem of
  * the entropy pool having similar initial state across largely
  * identical devices.
  */
 void add_device_randomness(const void *buf, size_t len)
 {
     unsigned long entropy = random_get_entropy();
     unsigned long flags;
 
     spin_lock_irqsave(&input_pool.lock, flags);
     _mix_pool_bytes(&entropy, sizeof(entropy));
     _mix_pool_bytes(buf, len);
     spin_unlock_irqrestore(&input_pool.lock, flags);
 }
 EXPORT_SYMBOL(add_device_randomness);
 
 /*
  * Interface for in-kernel drivers of true hardware RNGs.
  * Those devices may produce endless random bits and will be throttled
  * when our pool is full.
  */
 void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy)
 {
     mix_pool_bytes(buf, len);
     credit_init_bits(entropy);
 
     /*
      * Throttle writing to once every CRNG_RESEED_INTERVAL, unless
      * we're not yet initialized.
      */
     if (!kthread_should_stop() && crng_ready())
         schedule_timeout_interruptible(CRNG_RESEED_INTERVAL);
 }
 EXPORT_SYMBOL_GPL(add_hwgenerator_randomness);
 
 /*
  * Handle random seed passed by bootloader, and credit it if
  * CONFIG_RANDOM_TRUST_BOOTLOADER is set.
  */
 void __init add_bootloader_randomness(const void *buf, size_t len)
 {
     mix_pool_bytes(buf, len);
     if (trust_bootloader)
         credit_init_bits(len * 8);
 }
 
 #if IS_ENABLED(CONFIG_VMGENID)
 static BLOCKING_NOTIFIER_HEAD(vmfork_chain);
 
 /*
  * Handle a new unique VM ID, which is unique, not secret, so we
  * don't credit it, but we do immediately force a reseed after so
  * that it's used by the crng posthaste.
  */
 void __cold add_vmfork_randomness(const void *unique_vm_id, size_t len)
 {
     add_device_randomness(unique_vm_id, len);
     if (crng_ready()) {
         crng_reseed();
         pr_notice("crng reseeded due to virtual machine fork\n");
     }
     blocking_notifier_call_chain(&vmfork_chain, 0, NULL);
 }
 #if IS_MODULE(CONFIG_VMGENID)
 EXPORT_SYMBOL_GPL(add_vmfork_randomness);
 #endif
 
 int __cold register_random_vmfork_notifier(struct notifier_block *nb)
 {
     return blocking_notifier_chain_register(&vmfork_chain, nb);
 }
 EXPORT_SYMBOL_GPL(register_random_vmfork_notifier);
 
 int __cold unregister_random_vmfork_notifier(struct notifier_block *nb)
 {
     return blocking_notifier_chain_unregister(&vmfork_chain, nb);
 }
 EXPORT_SYMBOL_GPL(unregister_random_vmfork_notifier);
 #endif
 
 struct fast_pool {
     struct work_struct mix;
     unsigned long pool[4];
     unsigned long last;
     unsigned int count;
 };
 
 static DEFINE_PER_CPU(struct fast_pool, irq_randomness) = {
 #ifdef CONFIG_64BIT
 #define FASTMIX_PERM SIPHASH_PERMUTATION
     .pool = { SIPHASH_CONST_0, SIPHASH_CONST_1, SIPHASH_CONST_2, SIPHASH_CONST_3 }
 #else
 #define FASTMIX_PERM HSIPHASH_PERMUTATION
     .pool = { HSIPHASH_CONST_0, HSIPHASH_CONST_1, HSIPHASH_CONST_2, HSIPHASH_CONST_3 }
 #endif
 };
 
 /*
  * This is [Half]SipHash-1-x, starting from an empty key. Because
  * the key is fixed, it assumes that its inputs are non-malicious,
  * and therefore this has no security on its own. s represents the
  * four-word SipHash state, while v represents a two-word input.
  */
 static void fast_mix(unsigned long s[4], unsigned long v1, unsigned long v2)
 {
     s[3] ^= v1;
     FASTMIX_PERM(s[0], s[1], s[2], s[3]);
     s[0] ^= v1;
     s[3] ^= v2;
     FASTMIX_PERM(s[0], s[1], s[2], s[3]);
     s[0] ^= v2;
 }
 
 #ifdef CONFIG_SMP
 /*
  * This function is called when the CPU has just come online, with
  * entry CPUHP_AP_RANDOM_ONLINE, just after CPUHP_AP_WORKQUEUE_ONLINE.
  */
 int __cold random_online_cpu(unsigned int cpu)
 {
     /*
      * During CPU shutdown and before CPU onlining, add_interrupt_
      * randomness() may schedule mix_interrupt_randomness(), and
      * set the MIX_INFLIGHT flag. However, because the worker can
      * be scheduled on a different CPU during this period, that
      * flag will never be cleared. For that reason, we zero out
      * the flag here, which runs just after workqueues are onlined
      * for the CPU again. This also has the effect of setting the
      * irq randomness count to zero so that new accumulated irqs
      * are fresh.
      */
     per_cpu_ptr(&irq_randomness, cpu)->count = 0;
     return 0;
 }
 #endif
 
 static void mix_interrupt_randomness(struct work_struct *work)
 {
     struct fast_pool *fast_pool = container_of(work, struct fast_pool, mix);
     /*
      * The size of the copied stack pool is explicitly 2 longs so that we
      * only ever ingest half of the siphash output each time, retaining
      * the other half as the next "key" that carries over. The entropy is
      * supposed to be sufficiently dispersed between bits so on average
      * we don't wind up "losing" some.
      */
     unsigned long pool[2];
     unsigned int count;
 
     /* Check to see if we're running on the wrong CPU due to hotplug. */
     local_irq_disable();
     if (fast_pool != this_cpu_ptr(&irq_randomness)) {
         local_irq_enable();
         return;
     }
 
     /*
      * Copy the pool to the stack so that the mixer always has a
      * consistent view, before we reenable irqs again.
      */
     memcpy(pool, fast_pool->pool, sizeof(pool));
     count = fast_pool->count;
     fast_pool->count = 0;
     fast_pool->last = jiffies;
     local_irq_enable();
 
     mix_pool_bytes(pool, sizeof(pool));
     credit_init_bits(max(1u, (count & U16_MAX) / 64));
 
     memzero_explicit(pool, sizeof(pool));
 }
 
 void add_interrupt_randomness(int irq)
 {
     enum { MIX_INFLIGHT = 1U << 31 };
     unsigned long entropy = random_get_entropy();
     struct fast_pool *fast_pool = this_cpu_ptr(&irq_randomness);
     struct pt_regs *regs = get_irq_regs();
     unsigned int new_count;
 
     fast_mix(fast_pool->pool, entropy,
          (regs ? instruction_pointer(regs) : _RET_IP_) ^ swab(irq));
     new_count = ++fast_pool->count;
 
     if (new_count & MIX_INFLIGHT)
         return;
 
     if (new_count < 1024 && !time_is_before_jiffies(fast_pool->last + HZ))
         return;
 
     if (unlikely(!fast_pool->mix.func))
         INIT_WORK(&fast_pool->mix, mix_interrupt_randomness);
     fast_pool->count |= MIX_INFLIGHT;
     queue_work_on(raw_smp_processor_id(), system_highpri_wq, &fast_pool->mix);
 }
 EXPORT_SYMBOL_GPL(add_interrupt_randomness);
 
 /* There is one of these per entropy source */
 struct timer_rand_state {
     unsigned long last_time;
     long last_delta, last_delta2;
 };
 
 /*
  * This function adds entropy to the entropy "pool" by using timing
  * delays. It uses the timer_rand_state structure to make an estimate
  * of how many bits of entropy this call has added to the pool. The
  * value "num" is also added to the pool; it should somehow describe
  * the type of event that just happened.
  */
 static void add_timer_randomness(struct timer_rand_state *state, unsigned int num)
 {
     unsigned long entropy = random_get_entropy(), now = jiffies, flags;
     long delta, delta2, delta3;
     unsigned int bits;
 
     /*
      * If we're in a hard IRQ, add_interrupt_randomness() will be called
      * sometime after, so mix into the fast pool.
      */
     if (in_hardirq()) {
         fast_mix(this_cpu_ptr(&irq_randomness)->pool, entropy, num);
     } else {
         spin_lock_irqsave(&input_pool.lock, flags);
         _mix_pool_bytes(&entropy, sizeof(entropy));
         _mix_pool_bytes(&num, sizeof(num));
         spin_unlock_irqrestore(&input_pool.lock, flags);
     }
 
     if (crng_ready())
         return;
 
     /*
      * Calculate number of bits of randomness we probably added.
      * We take into account the first, second and third-order deltas
      * in order to make our estimate.
      */
     delta = now - READ_ONCE(state->last_time);
     WRITE_ONCE(state->last_time, now);
 
     delta2 = delta - READ_ONCE(state->last_delta);
     WRITE_ONCE(state->last_delta, delta);
 
     delta3 = delta2 - READ_ONCE(state->last_delta2);
     WRITE_ONCE(state->last_delta2, delta2);
 
     if (delta < 0)
         delta = -delta;
     if (delta2 < 0)
         delta2 = -delta2;
     if (delta3 < 0)
         delta3 = -delta3;
     if (delta > delta2)
         delta = delta2;
     if (delta > delta3)
         delta = delta3;
 
     /*
      * delta is now minimum absolute delta. Round down by 1 bit
      * on general principles, and limit entropy estimate to 11 bits.
      */
     bits = min(fls(delta >> 1), 11);
 
     /*
      * As mentioned above, if we're in a hard IRQ, add_interrupt_randomness()
      * will run after this, which uses a different crediting scheme of 1 bit
      * per every 64 interrupts. In order to let that function do accounting
      * close to the one in this function, we credit a full 64/64 bit per bit,
      * and then subtract one to account for the extra one added.
      */
     if (in_hardirq())
         this_cpu_ptr(&irq_randomness)->count += max(1u, bits * 64) - 1;
     else
         _credit_init_bits(bits);
 }
 
 void add_input_randomness(unsigned int type, unsigned int code, unsigned int value)
 {
     static unsigned char last_value;
     static struct timer_rand_state input_timer_state = { INITIAL_JIFFIES };
 
     /* Ignore autorepeat and the like. */
     if (value == last_value)
         return;
 
     last_value = value;
     add_timer_randomness(&input_timer_state,
                  (type << 4) ^ code ^ (code >> 4) ^ value);
 }
 EXPORT_SYMBOL_GPL(add_input_randomness);
 
 #ifdef CONFIG_BLOCK
 void add_disk_randomness(struct gendisk *disk)
 {
     if (!disk || !disk->random)
         return;
     /* First major is 1, so we get >= 0x200 here. */
     add_timer_randomness(disk->random, 0x100 + disk_devt(disk));
 }
 EXPORT_SYMBOL_GPL(add_disk_randomness);
 
 void __cold rand_initialize_disk(struct gendisk *disk)
 {
     struct timer_rand_state *state;
 
     /*
      * If kzalloc returns null, we just won't use that entropy
      * source.
      */
     state = kzalloc(sizeof(struct timer_rand_state), GFP_KERNEL);
     if (state) {
         state->last_time = INITIAL_JIFFIES;
         disk->random = state;
     }
 }
 #endif
 
 struct entropy_timer_state {
     unsigned long entropy;
     struct timer_list timer;
     unsigned int samples, samples_per_bit;
 };
 
 /*
  * Each time the timer fires, we expect that we got an unpredictable
  * jump in the cycle counter. Even if the timer is running on another
  * CPU, the timer activity will be touching the stack of the CPU that is
  * generating entropy..
  *
  * Note that we don't re-arm the timer in the timer itself - we are
  * happy to be scheduled away, since that just makes the load more
  * complex, but we do not want the timer to keep ticking unless the
  * entropy loop is running.
  *
  * So the re-arming always happens in the entropy loop itself.
  */
 static void __cold entropy_timer(struct timer_list *timer)
 {
     struct entropy_timer_state *state = container_of(timer, struct entropy_timer_state, timer);
 
     if (++state->samples == state->samples_per_bit) {
         credit_init_bits(1);
         state->samples = 0;
     }
 }
 
 /*
  * If we have an actual cycle counter, see if we can
  * generate enough entropy with timing noise
  */
 static void __cold try_to_generate_entropy(void)
 {
     enum { NUM_TRIAL_SAMPLES = 8192, MAX_SAMPLES_PER_BIT = HZ / 30 };
     struct entropy_timer_state stack;
     unsigned int i, num_different = 0;
     unsigned long last = random_get_entropy();
 
     for (i = 0; i < NUM_TRIAL_SAMPLES - 1; ++i) {
         stack.entropy = random_get_entropy();
         if (stack.entropy != last)
             ++num_different;
         last = stack.entropy;
     }
     stack.samples_per_bit = DIV_ROUND_UP(NUM_TRIAL_SAMPLES, num_different + 1);
     if (stack.samples_per_bit > MAX_SAMPLES_PER_BIT)
         return;
 
     stack.samples = 0;
     timer_setup_on_stack(&stack.timer, entropy_timer, 0);
     while (!crng_ready() && !signal_pending(current)) {
         if (!timer_pending(&stack.timer))
             mod_timer(&stack.timer, jiffies + 1);
         mix_pool_bytes(&stack.entropy, sizeof(stack.entropy));
         schedule();
         stack.entropy = random_get_entropy();
     }
 
     del_timer_sync(&stack.timer);
     destroy_timer_on_stack(&stack.timer);
     mix_pool_bytes(&stack.entropy, sizeof(stack.entropy));
 }
 
 
 /**********************************************************************
  *
  * Userspace reader/writer interfaces.
  *
  * getrandom(2) is the primary modern interface into the RNG and should
  * be used in preference to anything else.
  *
  * Reading from /dev/random has the same functionality as calling
  * getrandom(2) with flags=0. In earlier versions, however, it had
  * vastly different semantics and should therefore be avoided, to
  * prevent backwards compatibility issues.
  *
  * Reading from /dev/urandom has the same functionality as calling
  * getrandom(2) with flags=GRND_INSECURE. Because it does not block
  * waiting for the RNG to be ready, it should not be used.
  *
  * Writing to either /dev/random or /dev/urandom adds entropy to
  * the input pool but does not credit it.
  *
  * Polling on /dev/random indicates when the RNG is initialized, on
  * the read side, and when it wants new entropy, on the write side.
  *
  * Both /dev/random and /dev/urandom have the same set of ioctls for
  * adding entropy, getting the entropy count, zeroing the count, and
  * reseeding the crng.
  *
  **********************************************************************/
 
 SYSCALL_DEFINE3(getrandom, char __user *, ubuf, size_t, len, unsigned int, flags)
 {
     struct iov_iter iter;
     struct iovec iov;
     int ret;
 
     if (flags & ~(GRND_NONBLOCK | GRND_RANDOM | GRND_INSECURE))
         return -EINVAL;
 
     /*
      * Requesting insecure and blocking randomness at the same time makes
      * no sense.
      */
     if ((flags & (GRND_INSECURE | GRND_RANDOM)) == (GRND_INSECURE | GRND_RANDOM))
         return -EINVAL;
 
     if (!crng_ready() && !(flags & GRND_INSECURE)) {
         if (flags & GRND_NONBLOCK)
             return -EAGAIN;
         ret = wait_for_random_bytes();
         if (unlikely(ret))
             return ret;
     }
 
     ret = import_single_range(READ, ubuf, len, &iov, &iter);
     if (unlikely(ret))
         return ret;
     return get_random_bytes_user(&iter);
 }
 
 static __poll_t random_poll(struct file *file, poll_table *wait)
 {
     poll_wait(file, &crng_init_wait, wait);
     return crng_ready() ? EPOLLIN | EPOLLRDNORM : EPOLLOUT | EPOLLWRNORM;
 }
 
 static ssize_t write_pool_user(struct iov_iter *iter)
 {
     u8 block[BLAKE2S_BLOCK_SIZE];
     ssize_t ret = 0;
     size_t copied;
 
     if (unlikely(!iov_iter_count(iter)))
         return 0;
 
     for (;;) {
         copied = copy_from_iter(block, sizeof(block), iter);
         ret += copied;
         mix_pool_bytes(block, copied);
         if (!iov_iter_count(iter) || copied != sizeof(block))
             break;
 
         BUILD_BUG_ON(PAGE_SIZE % sizeof(block) != 0);
         if (ret % PAGE_SIZE == 0) {
             if (signal_pending(current))
                 break;
             cond_resched();
         }
     }
 
     memzero_explicit(block, sizeof(block));
     return ret ? ret : -EFAULT;
 }
 
 static ssize_t random_write_iter(struct kiocb *kiocb, struct iov_iter *iter)
 {
     return write_pool_user(iter);
 }
 
 static ssize_t urandom_read_iter(struct kiocb *kiocb, struct iov_iter *iter)
 {
     static int maxwarn = 10;
 
     /*
      * Opportunistically attempt to initialize the RNG on platforms that
      * have fast cycle counters, but don't (for now) require it to succeed.
      */
     if (!crng_ready())
         try_to_generate_entropy();
 
     if (!crng_ready()) {
         if (!ratelimit_disable && maxwarn <= 0)
             ++urandom_warning.missed;
         else if (ratelimit_disable || __ratelimit(&urandom_warning)) {
             --maxwarn;
             pr_notice("%s: uninitialized urandom read (%zu bytes read)\n",
                   current->comm, iov_iter_count(iter));
         }
     }
 
     return get_random_bytes_user(iter);
 }
 
 static ssize_t random_read_iter(struct kiocb *kiocb, struct iov_iter *iter)
 {
     int ret;
 
     ret = wait_for_random_bytes();
     if (ret != 0)
         return ret;
     return get_random_bytes_user(iter);
 }
 
 static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
 {
     int __user *p = (int __user *)arg;
     int ent_count;
 
     switch (cmd) {
     case RNDGETENTCNT:
         /* Inherently racy, no point locking. */
         if (put_user(input_pool.init_bits, p))
             return -EFAULT;
         return 0;
     case RNDADDTOENTCNT:
         if (!capable(CAP_SYS_ADMIN))
             return -EPERM;
         if (get_user(ent_count, p))
             return -EFAULT;
         if (ent_count < 0)
             return -EINVAL;
         credit_init_bits(ent_count);
         return 0;
     case RNDADDENTROPY: {
         struct iov_iter iter;
         struct iovec iov;
         ssize_t ret;
         int len;
 
         if (!capable(CAP_SYS_ADMIN))
             return -EPERM;
         if (get_user(ent_count, p++))
             return -EFAULT;
         if (ent_count < 0)
             return -EINVAL;
         if (get_user(len, p++))
             return -EFAULT;
         ret = import_single_range(WRITE, p, len, &iov, &iter);
         if (unlikely(ret))
             return ret;
         ret = write_pool_user(&iter);
         if (unlikely(ret < 0))
             return ret;
         /* Since we're crediting, enforce that it was all written into the pool. */
         if (unlikely(ret != len))
             return -EFAULT;
         credit_init_bits(ent_count);
         return 0;
     }
     case RNDZAPENTCNT:
     case RNDCLEARPOOL:
         /* No longer has any effect. */
         if (!capable(CAP_SYS_ADMIN))
             return -EPERM;
         return 0;
     case RNDRESEEDCRNG:
         if (!capable(CAP_SYS_ADMIN))
             return -EPERM;
         if (!crng_ready())
             return -ENODATA;
         crng_reseed();
         return 0;
     default:
         return -EINVAL;
     }
 }
 
 static int random_fasync(int fd, struct file *filp, int on)
 {
     return fasync_helper(fd, filp, on, &fasync);
 }
 
 const struct file_operations random_fops = {
     .read_iter = random_read_iter,
     .write_iter = random_write_iter,
     .poll = random_poll,
     .unlocked_ioctl = random_ioctl,
     .compat_ioctl = compat_ptr_ioctl,
     .fasync = random_fasync,
     .llseek = noop_llseek,
     .splice_read = generic_file_splice_read,
     .splice_write = iter_file_splice_write,
 };
 
 const struct file_operations urandom_fops = {
     .read_iter = urandom_read_iter,
     .write_iter = random_write_iter,
     .unlocked_ioctl = random_ioctl,
     .compat_ioctl = compat_ptr_ioctl,
     .fasync = random_fasync,
     .llseek = noop_llseek,
     .splice_read = generic_file_splice_read,
     .splice_write = iter_file_splice_write,
 };
 
 
 /********************************************************************
  *
  * Sysctl interface.
  *
  * These are partly unused legacy knobs with dummy values to not break
  * userspace and partly still useful things. They are usually accessible
  * in /proc/sys/kernel/random/ and are as follows:
  *
  * - boot_id - a UUID representing the current boot.
  *
  * - uuid - a random UUID, different each time the file is read.
  *
  * - poolsize - the number of bits of entropy that the input pool can
  *   hold, tied to the POOL_BITS constant.
  *
  * - entropy_avail - the number of bits of entropy currently in the
  *   input pool. Always <= poolsize.
  *
  * - write_wakeup_threshold - the amount of entropy in the input pool
  *   below which write polls to /dev/random will unblock, requesting
  *   more entropy, tied to the POOL_READY_BITS constant. It is writable
  *   to avoid breaking old userspaces, but writing to it does not
  *   change any behavior of the RNG.
  *
  * - urandom_min_reseed_secs - fixed to the value CRNG_RESEED_INTERVAL.
  *   It is writable to avoid breaking old userspaces, but writing
  *   to it does not change any behavior of the RNG.
  *
  ********************************************************************/
 
 #ifdef CONFIG_SYSCTL
 
 #include <linux/sysctl.h>
 
 static int sysctl_random_min_urandom_seed = CRNG_RESEED_INTERVAL / HZ;
 static int sysctl_random_write_wakeup_bits = POOL_READY_BITS;
 static int sysctl_poolsize = POOL_BITS;
 static u8 sysctl_bootid[UUID_SIZE];
 
 /*
  * This function is used to return both the bootid UUID, and random
  * UUID. The difference is in whether table->data is NULL; if it is,
  * then a new UUID is generated and returned to the user.
  */
 static int proc_do_uuid(struct ctl_table *table, int write, void *buf,
             size_t *lenp, loff_t *ppos)
 {
     u8 tmp_uuid[UUID_SIZE], *uuid;
     char uuid_string[UUID_STRING_LEN + 1];
     struct ctl_table fake_table = {
         .data = uuid_string,
         .maxlen = UUID_STRING_LEN
     };
 
     if (write)
         return -EPERM;
 
     uuid = table->data;
     if (!uuid) {
         uuid = tmp_uuid;
         generate_random_uuid(uuid);
     } else {
         static DEFINE_SPINLOCK(bootid_spinlock);
 
         spin_lock(&bootid_spinlock);
         if (!uuid[8])
             generate_random_uuid(uuid);
         spin_unlock(&bootid_spinlock);
     }
 
     snprintf(uuid_string, sizeof(uuid_string), "%pU", uuid);
     return proc_dostring(&fake_table, 0, buf, lenp, ppos);
 }
 
 /* The same as proc_dointvec, but writes don't change anything. */
 static int proc_do_rointvec(struct ctl_table *table, int write, void *buf,
                 size_t *lenp, loff_t *ppos)
 {
     return write ? 0 : proc_dointvec(table, 0, buf, lenp, ppos);
 }
 
 static struct ctl_table random_table[] = {
     {
         .procname   = "poolsize",
         .data       = &sysctl_poolsize,
         .maxlen     = sizeof(int),
         .mode       = 0444,
         .proc_handler   = proc_dointvec,
     },
     {
         .procname   = "entropy_avail",
         .data       = &input_pool.init_bits,
         .maxlen     = sizeof(int),
         .mode       = 0444,
         .proc_handler   = proc_dointvec,
     },
     {
         .procname   = "write_wakeup_threshold",
         .data       = &sysctl_random_write_wakeup_bits,
         .maxlen     = sizeof(int),
         .mode       = 0644,
         .proc_handler   = proc_do_rointvec,
     },
     {
         .procname   = "urandom_min_reseed_secs",
         .data       = &sysctl_random_min_urandom_seed,
         .maxlen     = sizeof(int),
         .mode       = 0644,
         .proc_handler   = proc_do_rointvec,
     },
     {
         .procname   = "boot_id",
         .data       = &sysctl_bootid,
         .mode       = 0444,
         .proc_handler   = proc_do_uuid,
     },
     {
         .procname   = "uuid",
         .mode       = 0444,
         .proc_handler   = proc_do_uuid,
     },
     { }
 };
 
 /*
  * random_init() is called before sysctl_init(),
  * so we cannot call register_sysctl_init() in random_init()
  */
 static int __init random_sysctls_init(void)
 {
     register_sysctl_init("kernel/random", random_table);
     return 0;
 }
 device_initcall(random_sysctls_init);
 #endif

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