android/android_kernel_asus_sm8350
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random: fix data race on crng init time

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commit 009ba8568be497c640cab7571f7bfd18345d7b24 upstream.

_extract_crng() does plain loads of crng->init_time and
crng_global_init_time, which causes undefined behavior if
crng_reseed() and RNDRESEEDCRNG modify these corrently.

Use READ_ONCE() and WRITE_ONCE() to make the behavior defined.

Don't fix the race on crng->init_time by protecting it with crng->lock,
since it's not a problem for duplicate reseedings to occur.  I.e., the
lockless access with READ_ONCE() is fine.

Fixes: d848e5f8e1 ("random: add new ioctl RNDRESEEDCRNG")
Fixes: e192be9d9a ("random: replace non-blocking pool with a Chacha20-based CRNG")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Eric Biggers 2021-12-20 16:41:57 -06:00 committed by Greg Kroah-Hartman
parent 90ceecdaa0
commit 517ab153f5
1 changed files with 10 additions and 7 deletions
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17
drivers/char/random.c
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@ -1042,7 +1042,7 @@ static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
crng->state[i+4] ^= buf.key[i] ^ rv;
}
memzero_explicit(&buf, sizeof(buf));
crng->init_time = jiffies;
WRITE_ONCE(crng->init_time, jiffies);
spin_unlock_irqrestore(&crng->lock, flags);
if (crng == &primary_crng && crng_init < 2) {
invalidate_batched_entropy();
@ -1069,12 +1069,15 @@ static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
static void _extract_crng(struct crng_state *crng,
__u8 out[CHACHA_BLOCK_SIZE])
{
unsigned long v, flags;
unsigned long v, flags, init_time;
if (crng_ready() &&
(time_after(crng_global_init_time, crng->init_time) ||
time_after(jiffies, crng->init_time + CRNG_RESEED_INTERVAL)))
crng_reseed(crng, crng == &primary_crng ? &input_pool : NULL);
if (crng_ready()) {
init_time = READ_ONCE(crng->init_time);
if (time_after(READ_ONCE(crng_global_init_time), init_time) ||
time_after(jiffies, init_time + CRNG_RESEED_INTERVAL))
crng_reseed(crng, crng == &primary_crng ?
&input_pool : NULL);
}
spin_lock_irqsave(&crng->lock, flags);
if (arch_get_random_long(&v))
crng->state[14] ^= v;
@ -2152,7 +2155,7 @@ static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
if (crng_init < 2)
return -ENODATA;
crng_reseed(&primary_crng, &input_pool);
crng_global_init_time = jiffies - 1;
WRITE_ONCE(crng_global_init_time, jiffies - 1);
return 0;
default:
return -EINVAL;