diff options
| author | Eric Biggers <ebiggers@google.com> | 2021-12-21 01:41:57 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-01-16 11:14:23 +0300 |
| commit | 61cca7d191c7c143bc8f3e779859f8b3d5100c89 (patch) | |
| tree | 85364bb198918ae700ea50830e894b22a67844ff | |
| parent | 3de9478230c3e3ae0ae599847ca2ac6b7781e780 (diff) | |
| download | linux-61cca7d191c7c143bc8f3e779859f8b3d5100c89.tar.xz | |
random: fix data race on crng init time
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: d848e5f8e1eb ("random: add new ioctl RNDRESEEDCRNG")
Fixes: e192be9d9a30 ("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>
| -rw-r--r-- | drivers/char/random.c | 17 |
1 files changed, 10 insertions, 7 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c index 08947733b555..904ba49a9158 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -990,7 +990,7 @@ 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(); @@ -1016,12 +1016,15 @@ 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; @@ -1975,7 +1978,7 @@ 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; |