random: avoid initializing twice in credit race

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commit fed7ef0616 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@dominikbrodowski.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

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Jason A. Donenfeld 2022-05-09 13:40:55 +02:00 • committed by Greg Kroah-Hartman

parent 23a1b984f4

commit c4e600154a

1 changed files with 5 additions and 5 deletions

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drivers/char/random.c

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