linux-kernel - [BUG][PATCH] audit: audit_log_start running on auditd should not stop

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Message-ID: <20131015134345.98d72df42a39e9e1ad77a73c@jp.fujitsu.com>
Date:	Tue, 15 Oct 2013 13:43:45 +0900
From:	Toshiyuki Okajima <toshi.okajima@...fujitsu.com>
To:	Gao feng <gaofeng@...fujitsu.com>, <viro@...iv.linux.org.uk>,
	<eparis@...hat.com>
CC:	<toshi.okajima@...fujitsu.com>, <linux-kernel@...r.kernel.org>
Subject: [BUG][PATCH] audit: audit_log_start running on auditd should not
 stop

The backlog cannot be consumed when audit_log_start is running on auditd
even if audit_log_start calls wait_for_auditd to consume it.
The situation is a deadlock because only auditd can consume the backlog.
If the other process needs to send the backlog, it can be also stopped 
by the deadlock.

So, audit_log_start running on auditd should not stop.

You can see the deadlock with the following reproducer:
 # auditctl -a exit,always -S all
 # reboot

Signed-off-by: Toshiyuki Okajima <toshi.okajima@...fujitsu.com>
Cc: gaofeng@...fujitsu.com
---
 kernel/audit.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/kernel/audit.c b/kernel/audit.c
index 7b0e23a..ce1fb38 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -1098,6 +1098,9 @@ struct audit_buffer *audit_log_start(struct audit_context *ctx, gfp_t gfp_mask,
 	int reserve;
 	unsigned long timeout_start = jiffies;
 
+	if (audit_pid && audit_pid == current->pid)
+		gfp_mask &= ~__GFP_WAIT;
+
 	if (audit_initialized != AUDIT_INITIALIZED)
 		return NULL;
 
-- 
1.5.5.6
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