3.13-stable review patch. If anyone has any objections, please let me know.
------------------
From: Sasha Levin <sasha.levin@xxxxxxxxxx>
commit 05efa8c943b1d5d90fa8c8147571837573338bb6 upstream.
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 <sasha.levin@xxxxxxxxxx>
Acked-by: Hannes Frederic Sowa <hannes@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Daniel Borkmann <dborkman@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
lib/random32.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
--- 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;
--
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