From: Jeff Moyer <jmoyer@redhat.com>
Date: Tue, 3 Dec 2013 21:23:00 +0000 (-0700)
Subject: blk-mq: fix dereference of rq->mq_ctx if allocation fails
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=959a35f13eb785f982d79b1aaa75872d05c821da;p=openwrt%2Fstaging%2Fblogic.git

blk-mq: fix dereference of rq->mq_ctx if allocation fails

If __GFP_WAIT isn't set and we fail allocating, when we go
to drop the reference on the ctx, we will attempt to dereference
the NULL rq. Fix that.

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/block/blk-mq.c b/block/blk-mq.c
index cdc629cf075b..70fd6f996600 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -202,10 +202,12 @@ static struct request *blk_mq_alloc_request_pinned(struct request_queue *q,
 		if (rq) {
 			blk_mq_rq_ctx_init(q, ctx, rq, rw);
 			break;
-		} else if (!(gfp & __GFP_WAIT))
-			break;
+		}
 
 		blk_mq_put_ctx(ctx);
+		if (!(gfp & __GFP_WAIT))
+			break;
+
 		__blk_mq_run_hw_queue(hctx);
 		blk_mq_wait_for_tags(hctx->tags);
 	} while (1);
@@ -222,7 +224,8 @@ struct request *blk_mq_alloc_request(struct request_queue *q, int rw,
 		return NULL;
 
 	rq = blk_mq_alloc_request_pinned(q, rw, gfp, reserved);
-	blk_mq_put_ctx(rq->mq_ctx);
+	if (rq)
+		blk_mq_put_ctx(rq->mq_ctx);
 	return rq;
 }
 
@@ -235,7 +238,8 @@ struct request *blk_mq_alloc_reserved_request(struct request_queue *q, int rw,
 		return NULL;
 
 	rq = blk_mq_alloc_request_pinned(q, rw, gfp, true);
-	blk_mq_put_ctx(rq->mq_ctx);
+	if (rq)
+		blk_mq_put_ctx(rq->mq_ctx);
 	return rq;
 }
 EXPORT_SYMBOL(blk_mq_alloc_reserved_request);