Commit 4d5151cc authored Feb 22, 2022 by Jason A. Donenfeld Committed by Greg Kroah-Hartman Jun 22, 2022

random: only wake up writers after zap if threshold was passed



commit a3f9e8910e1584d7725ef7d5ac870920d42d0bb4 upstream.

The only time that we need to wake up /dev/random writers on
RNDCLEARPOOL/RNDZAPPOOL is when we're changing from a value that is
greater than or equal to POOL_MIN_BITS to zero, because if we're
changing from below POOL_MIN_BITS to zero, the writers are already
unblocked.

Cc: Theodore Ts'o <tytso@mit.edu>
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>

parent ac0081de

drivers/char/random.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1577,7 +1577,7 @@ static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
		*/
		if (!capable(CAP_SYS_ADMIN))
		return -EPERM;
		if (xchg(&input_pool.entropy_count, 0)) {
		if (xchg(&input_pool.entropy_count, 0) >= POOL_MIN_BITS) {
		wake_up_interruptible(&random_write_wait);
		kill_fasync(&fasync, SIGIO, POLL_OUT);
		}