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random: wake up /dev/random writers after zap

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[ Upstream commit 042e293e16 ]

When account() is called, and the amount of entropy dips below
random_write_wakeup_bits, we wake up the random writers, so that they
can write some more in. However, the RNDZAPENTCNT/RNDCLEARPOOL ioctl
sets the entropy count to zero -- a potential reduction just like
account() -- but does not unblock writers. This commit adds the missing
logic to that ioctl to unblock waiting writers.

Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Jason A. Donenfeld 2022-01-28 23:44:03 +01:00 committed by Greg Kroah-Hartman
parent effdcc2505
commit b16817a6de
1 changed files with 4 additions and 1 deletions
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5
drivers/char/random.c
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@ -1963,7 +1963,10 @@ static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
*/
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
input_pool.entropy_count = 0;
if (xchg(&input_pool.entropy_count, 0) && random_write_wakeup_bits) {
wake_up_interruptible(&random_write_wait);
kill_fasync(&fasync, SIGIO, POLL_OUT);
}
return 0;
case RNDRESEEDCRNG:
if (!capable(CAP_SYS_ADMIN))