linux-kernel - [UNTESTED PATCH] block: fix a potential null pointer dereference

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Date:   Fri, 24 May 2019 13:35:20 +0800
From:   Peng Wang <rocking@....edu.cn>
To:     axboe@...nel.dk
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Peng Wang <rocking@....edu.cn>
Subject: [UNTESTED PATCH] block: fix a potential null pointer dereference

blk_queue_dying() still needs request_queue "q" when
enter_succeeded is false, so let's set "q" zero later.

Signed-off-by: Peng Wang <rocking@....edu.cn>
---
 block/blk-core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 419d600e6637..3d43909db3b8 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1056,7 +1056,6 @@ blk_qc_t generic_make_request(struct bio *bio)
 				flags = BLK_MQ_REQ_NOWAIT;
 			if (blk_queue_enter(q, flags) < 0) {
 				enter_succeeded = false;
-				q = NULL;
 			}
 		}
 
@@ -1088,6 +1087,7 @@ blk_qc_t generic_make_request(struct bio *bio)
 				bio_wouldblock_error(bio);
 			else
 				bio_io_error(bio);
+			q = NULL;
 		}
 		bio = bio_list_pop(&bio_list_on_stack[0]);
 	} while (bio);
-- 
2.19.1