Commit 05efa8c9 authored Mar 28, 2014 by Sasha Levin Committed by David S. Miller Mar 28, 2014

random32: avoid attempt to late reseed if in the middle of seeding

Commit 4af712e8 ("random32: add prandom_reseed_late() and call when
nonblocking pool becomes initialized") has added a late reseed stage
that happens as soon as the nonblocking pool is marked as initialized.

This fails in the case that the nonblocking pool gets initialized
during __prandom_reseed()'s call to get_random_bytes(). In that case
we'd double back into __prandom_reseed() in an attempt to do a late
reseed - deadlocking on 'lock' early on in the boot process.

Instead, just avoid even waiting to do a reseed if a reseed is already
occuring.

Fixes: 4af712e8 ("random32: add prandom_reseed_late() and call when nonblocking pool becomes initialized")
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 335a67d2

lib/random32.c

+12 −1

Original line number	Diff line number	Diff line
		@@ -244,8 +244,19 @@ static void __prandom_reseed(bool late)
		static bool latch = false;
		static DEFINE_SPINLOCK(lock);

		/* Asking for random bytes might result in bytes getting
		* moved into the nonblocking pool and thus marking it
		* as initialized. In this case we would double back into
		* this function and attempt to do a late reseed.
		* Ignore the pointless attempt to reseed again if we're
		* already waiting for bytes when the nonblocking pool
		* got initialized.
		*/

		/* only allow initial seeding (late == false) once */
		spin_lock_irqsave(&lock, flags);
		if (!spin_trylock_irqsave(&lock, flags))
		return;

		if (latch && !late)
		goto out;
		latch = true;