This is a note to let you know that I've just added the patch titled
random: avoid initializing twice in credit race
to the 5.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
random-avoid-initializing-twice-in-credit-race.patch
and it can be found in the queue-5.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Thu May 26 04:17:01 PM CEST 2022
From: "Jason A. Donenfeld" <Jason@xxxxxxxxx>
Date: Mon, 9 May 2022 13:40:55 +0200
Subject: random: avoid initializing twice in credit race
From: "Jason A. Donenfeld" <Jason@xxxxxxxxx>
commit fed7ef061686cc813b1f3d8d0edc6c35b4d3537b upstream.
Since all changes of crng_init now go through credit_init_bits(), we can
fix a long standing race in which two concurrent callers of
credit_init_bits() have the new bit count >= some threshold, but are
doing so with crng_init as a lower threshold, checked outside of a lock,
resulting in crng_reseed() or similar being called twice.
In order to fix this, we can use the original cmpxchg value of the bit
count, and only change crng_init when the bit count transitions from
below a threshold to meeting the threshold.
Reviewed-by: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/char/random.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -821,7 +821,7 @@ static void extract_entropy(void *buf, s
static void credit_init_bits(size_t nbits)
{
- unsigned int init_bits, orig, add;
+ unsigned int new, orig, add;
unsigned long flags;
if (crng_ready() || !nbits)
@@ -831,12 +831,12 @@ static void credit_init_bits(size_t nbit
do {
orig = READ_ONCE(input_pool.init_bits);
- init_bits = min_t(unsigned int, POOL_BITS, orig + add);
- } while (cmpxchg(&input_pool.init_bits, orig, init_bits) != orig);
+ new = min_t(unsigned int, POOL_BITS, orig + add);
+ } while (cmpxchg(&input_pool.init_bits, orig, new) != orig);
- if (!crng_ready() && init_bits >= POOL_READY_BITS)
+ if (orig < POOL_READY_BITS && new >= POOL_READY_BITS)
crng_reseed();
- else if (unlikely(crng_init == CRNG_EMPTY && init_bits >= POOL_EARLY_BITS)) {
+ else if (orig < POOL_EARLY_BITS && new >= POOL_EARLY_BITS) {
spin_lock_irqsave(&base_crng.lock, flags);
if (crng_init == CRNG_EMPTY) {
extract_entropy(base_crng.key, sizeof(base_crng.key));
Patches currently in stable-queue which might be from Jason@xxxxxxxxx are
queue-5.18/random-remove-ratelimiting-for-in-kernel-unseeded-randomness.patch
queue-5.18/random-fix-sysctl-documentation-nits.patch
queue-5.18/random-help-compiler-out-with-fast_mix-by-using-simpler-arguments.patch
queue-5.18/siphash-use-one-source-of-truth-for-siphash-permutations.patch
queue-5.18/um-use-fallback-for-random_get_entropy-instead-of-zero.patch
queue-5.18/random-order-timer-entropy-functions-below-interrupt-functions.patch
queue-5.18/random-unify-batched-entropy-implementations.patch
queue-5.18/random-make-consistent-use-of-buf-and-len.patch
queue-5.18/random-move-randomize_page-into-mm-where-it-belongs.patch
queue-5.18/random-use-first-128-bits-of-input-as-fast-init.patch
queue-5.18/random-use-proper-return-types-on-get_random_-int-long-_wait.patch
queue-5.18/s390-define-get_cycles-macro-for-arch-override.patch
queue-5.18/timekeeping-add-raw-clock-fallback-for-random_get_entropy.patch
queue-5.18/random-use-static-branch-for-crng_ready.patch
queue-5.18/arm-use-fallback-for-random_get_entropy-instead-of-zero.patch
queue-5.18/mips-use-fallback-for-random_get_entropy-instead-of-just-c0-random.patch
queue-5.18/random-avoid-initializing-twice-in-credit-race.patch
queue-5.18/random-move-initialization-functions-out-of-hot-pages.patch
queue-5.18/random-do-not-pretend-to-handle-premature-next-security-model.patch
queue-5.18/random-do-not-use-batches-when-crng_ready.patch
queue-5.18/m68k-use-fallback-for-random_get_entropy-instead-of-zero.patch
queue-5.18/random-move-initialization-out-of-reseeding-hot-path.patch
queue-5.18/x86-tsc-use-fallback-for-random_get_entropy-instead-of-zero.patch
queue-5.18/random-credit-architectural-init-the-exact-amount.patch
queue-5.18/random-check-for-signals-after-page-of-pool-writes.patch
queue-5.18/random-remove-extern-from-functions-in-header.patch
queue-5.18/random-do-not-use-input-pool-from-hard-irqs.patch
queue-5.18/random-wire-up-fops-splice_-read-write-_iter.patch
queue-5.18/random-insist-on-random_get_entropy-existing-in-order-to-simplify.patch
queue-5.18/powerpc-define-get_cycles-macro-for-arch-override.patch
queue-5.18/parisc-define-get_cycles-macro-for-arch-override.patch
queue-5.18/sparc-use-fallback-for-random_get_entropy-instead-of-zero.patch
queue-5.18/nios2-use-fallback-for-random_get_entropy-instead-of-zero.patch
queue-5.18/init-call-time_init-before-rand_initialize.patch
queue-5.18/riscv-use-fallback-for-random_get_entropy-instead-of-zero.patch
queue-5.18/ia64-define-get_cycles-macro-for-arch-override.patch
queue-5.18/random-handle-latent-entropy-and-command-line-from-random_init.patch
queue-5.18/random-use-proper-jiffies-comparison-macro.patch
queue-5.18/alpha-define-get_cycles-macro-for-arch-override.patch
queue-5.18/random-convert-to-using-fops-read_iter.patch
queue-5.18/xtensa-use-fallback-for-random_get_entropy-instead-of-zero.patch
queue-5.18/random-use-symbolic-constants-for-crng_init-states.patch
queue-5.18/random-convert-to-using-fops-write_iter.patch
