[PATCH] random32: assign to network folks in MAINTAINERS

[PATCH] random32: assign to network folks in MAINTAINERS

[Sasha Levin]

lib/random32.c was split out of the network code and is de-facto
still maintained by the almighty net/ gods.

Make it a bit more official so that people who aren't aware of
that know where to send their patches.

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
---
 MAINTAINERS | 1 +
 1 file changed, 1 insertion(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index e1724d5..47fd188 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -6091,6 +6091,7 @@ F:	include/uapi/linux/net.h
 F:	include/uapi/linux/netdevice.h
 F:	tools/net/
 F:	tools/testing/selftests/net/
+F:	lib/random32.c
 
 NETWORKING [IPv4/IPv6]
 M:	"David S. Miller" <davem@davemloft.net>
-- 
1.8.3.2

[PATCH v2] random32: avoid attempt to late reseed if in the middle of seeding

[Sasha Levin]

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(-)

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;
 
-- 
1.8.3.2

Re: [PATCH v2] random32: avoid attempt to late reseed if in the middle of seeding

[Hannes Frederic Sowa]

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>

Re: [PATCH v2] random32: avoid attempt to late reseed if in the middle of seeding

[Daniel Borkmann]

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>

Re: [PATCH] random32: assign to network folks in MAINTAINERS

[David Miller]

From: Sasha Levin <sasha.levin@oracle.com>
Date: Thu, 27 Mar 2014 02:01:34 -0400

> lib/random32.c was split out of the network code and is de-facto
> still maintained by the almighty net/ gods.
> 
> Make it a bit more official so that people who aren't aware of
> that know where to send their patches.
> 
> Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

Applied.