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Fix a BUG splat found by trinity.

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Merge tag 'random_for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random

Pull /dev/random fix from Ted Ts'o:
 "Fix a BUG splat found by trinity"

* tag 'random_for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random:
  random: check for increase of entropy_count because of signed conversion
This commit is contained in:
Linus Torvalds 2014-07-18 20:26:46 -10:00
commit b8d2d12804
1 changed files with 14 additions and 3 deletions
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17
drivers/char/random.c
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@ -641,7 +641,7 @@ static void credit_entropy_bits(struct entropy_store *r, int nbits)
} while (unlikely(entropy_count < pool_size-2 && pnfrac));
}
if (entropy_count < 0) {
if (unlikely(entropy_count < 0)) {
pr_warn("random: negative entropy/overflow: pool %s count %d\n",
r->name, entropy_count);
WARN_ON(1);
@ -981,7 +981,7 @@ static size_t account(struct entropy_store *r, size_t nbytes, int min,
int reserved)
{
int entropy_count, orig;
size_t ibytes;
size_t ibytes, nfrac;
BUG_ON(r->entropy_count > r->poolinfo->poolfracbits);
@ -999,7 +999,17 @@ static size_t account(struct entropy_store *r, size_t nbytes, int min,
}
if (ibytes < min)
ibytes = 0;
if ((entropy_count -= ibytes << (ENTROPY_SHIFT + 3)) < 0)
if (unlikely(entropy_count < 0)) {
pr_warn("random: negative entropy count: pool %s count %d\n",
r->name, entropy_count);
WARN_ON(1);
entropy_count = 0;
}
nfrac = ibytes << (ENTROPY_SHIFT + 3);
if ((size_t) entropy_count > nfrac)
entropy_count -= nfrac;
else
entropy_count = 0;
if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
@ -1376,6 +1386,7 @@ urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
"with %d bits of entropy available\n",
current->comm, nonblocking_pool.entropy_total);
nbytes = min_t(size_t, nbytes, INT_MAX >> (ENTROPY_SHIFT + 3));
ret = extract_entropy_user(&nonblocking_pool, buf, nbytes);
trace_urandom_read(8 * nbytes, ENTROPY_BITS(&nonblocking_pool),