From: Oleg Nesterov <oleg@tv-sign.ru>
Date: Tue, 23 Oct 2007 13:08:21 +0000 (+0200)
Subject: cfq_get_queue: fix possible NULL pointer access
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=0a0836a09ca7a27341703ef154c82e2e7f3e96f4;p=linux-beck.git

cfq_get_queue: fix possible NULL pointer access

cfq_get_queue()->cfq_find_alloc_queue() can fail, check the returned value.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>

Note that this isn't a bug at the moment, since the regular IO path
does not call this path without __GFP_WAIT set. However, it could be a
future bug, so I've applied it.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---

diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index d77c9719b613..e47a9309eb48 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1443,8 +1443,11 @@ cfq_get_queue(struct cfq_data *cfqd, int is_sync, struct task_struct *tsk,
 		cfqq = *async_cfqq;
 	}
 
-	if (!cfqq)
+	if (!cfqq) {
 		cfqq = cfq_find_alloc_queue(cfqd, is_sync, tsk, gfp_mask);
+		if (!cfqq)
+			return NULL;
+	}
 
 	/*
 	 * pin the queue now that it's allocated, scheduler exit will prune it