From: Sasha Levin Date: Fri, 28 Mar 2014 16:38:42 +0000 (+0100) Subject: random32: avoid attempt to late reseed if in the middle of seeding X-Git-Url: http://pileus.org/git/?p=~andy%2Flinux;a=commitdiff_plain;h=05efa8c943b1d5d90fa8c8147571837573338bb6;hp=335a67d2ad481b03607bf30a38c28178fa1ad61a random32: avoid attempt to late reseed if in the middle of seeding Commit 4af712e8df ("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: 4af712e8df99 ("random32: add prandom_reseed_late() and call when nonblocking pool becomes initialized") Signed-off-by: Sasha Levin Acked-by: Hannes Frederic Sowa Signed-off-by: Daniel Borkmann Signed-off-by: David S. Miller --- diff --git a/lib/random32.c b/lib/random32.c index 1e5b2df4429..61489677870 100644 --- a/lib/random32.c +++ b/lib/random32.c @@ -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;