| Message ID | 1395900095-15254-2-git-send-email-sasha.levin@oracle.com |
|---|---|
| State | Superseded, archived |
| Delegated to: | David Miller |
| Headers | show |
On Thu, Mar 27, 2014 at 02:01:35AM -0400, Sasha Levin wrote: > 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. > > Signed-off-by: Sasha Levin <sasha.levin@oracle.com> Thanks for fixing this! Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org> -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 03/27/2014 07:01 AM, Sasha Levin wrote: > 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. > > Signed-off-by: Sasha Levin <sasha.levin@oracle.com> Looks better now, thanks! Fixes: 4af712e8df99 ("random32: add prandom_reseed_late() and call when nonblocking pool becomes initialized") Acked-by: Daniel Borkmann <dborkman@redhat.com> -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/lib/random32.c b/lib/random32.c index b33b23e..d67b6a7 100644 --- a/lib/random32.c +++ b/lib/random32.c @@ -245,8 +245,20 @@ 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;
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. Signed-off-by: Sasha Levin <sasha.levin@oracle.com> --- lib/random32.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-)