[ 3.5.y.z extended stable ] Patch "audit: wait_for_auditd() should use TASK_UNINTERRUPTIBLE" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    audit: wait_for_auditd() should use TASK_UNINTERRUPTIBLE

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 10dc873a348efb942fe03cc4b4559d7b6c3c8ac3 Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg at redhat.com>
Date: Wed, 12 Jun 2013 14:04:46 -0700
Subject: [PATCH] audit: wait_for_auditd() should use TASK_UNINTERRUPTIBLE

commit f000cfdde5de4fc15dead5ccf524359c07eadf2b upstream.

audit_log_start() does wait_for_auditd() in a loop until
audit_backlog_wait_time passes or audit_skb_queue has a room.

If signal_pending() is true this becomes a busy-wait loop, schedule() in
TASK_INTERRUPTIBLE won't block.

Thanks to Guy for fully investigating and explaining the problem.

(akpm: that'll cause the system to lock up on a non-preemptible
uniprocessor kernel)

(Guy: "Our customer was in fact running a uniprocessor machine, and they
reported a system hang.")

Signed-off-by: Oleg Nesterov <oleg at redhat.com>
Reported-by: Guy Streeter <streeter at redhat.com>
Cc: Eric Paris <eparis at redhat.com>
Cc: Al Viro <viro at zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
[ luis: backported to 3.5: adjust context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 kernel/audit.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/audit.c b/kernel/audit.c
index 1c7f2c6..5917dfe 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1167,7 +1167,7 @@ struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask,

 			/* Wait for auditd to drain the queue a little */
 			DECLARE_WAITQUEUE(wait, current);
-			set_current_state(TASK_INTERRUPTIBLE);
+			set_current_state(TASK_UNINTERRUPTIBLE);
 			add_wait_queue(&audit_backlog_wait, &wait);

 			if (audit_backlog_limit &&
--
1.8.1.2