From: Yu Kuai <yukuai1@huaweicloud.com>
To: axboe@kernel.dk, ming.lei@redhat.com, hare@suse.de,
john.garry@huawei.com
Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
yukuai3@huawei.com, yukuai1@huaweicloud.com, yi.zhang@huawei.com
Subject: [PATCH v2] blk-mq: fix null pointer dereference in blk_mq_clear_rq_mapping()
Date: Tue, 11 Oct 2022 22:22:53 +0800 [thread overview]
Message-ID: <20221011142253.4015966-1-yukuai1@huaweicloud.com> (raw)
From: Yu Kuai <yukuai3@huawei.com>
Our syzkaller report a null pointer dereference, root cause is
following:
__blk_mq_alloc_map_and_rqs
set->tags[hctx_idx] = blk_mq_alloc_map_and_rqs
blk_mq_alloc_map_and_rqs
blk_mq_alloc_rqs
// failed due to oom
alloc_pages_node
// set->tags[hctx_idx] is still NULL
blk_mq_free_rqs
drv_tags = set->tags[hctx_idx];
// null pointer dereference is triggered
blk_mq_clear_rq_mapping(drv_tags, ...)
This is because commit 63064be150e4 ("blk-mq:
Add blk_mq_alloc_map_and_rqs()") merged the two steps:
1) set->tags[hctx_idx] = blk_mq_alloc_rq_map()
2) blk_mq_alloc_rqs(..., set->tags[hctx_idx])
into one step:
set->tags[hctx_idx] = blk_mq_alloc_map_and_rqs()
Since tags is not initialized yet in this case, fix the problem by
checking if tags is NULL pointer in blk_mq_clear_rq_mapping().
Fixes: 63064be150e4 ("blk-mq: Add blk_mq_alloc_map_and_rqs()")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: John Garry <john.garry@huawei.com>
---
Changes in v2:
- fix spelling mistakes
- add review tag
block/blk-mq.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 8070b6c10e8d..33292c01875d 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3112,8 +3112,11 @@ static void blk_mq_clear_rq_mapping(struct blk_mq_tags *drv_tags,
struct page *page;
unsigned long flags;
- /* There is no need to clear a driver tags own mapping */
- if (drv_tags == tags)
+ /*
+ * There is no need to clear mapping if driver tags is not initialized
+ * or the mapping belongs to the driver tags.
+ */
+ if (!drv_tags || drv_tags == tags)
return;
list_for_each_entry(page, &tags->page_list, lru) {
--
2.31.1
next reply other threads:[~2022-10-11 14:00 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-11 14:22 Yu Kuai [this message]
2022-10-15 3:58 ` [PATCH v2] blk-mq: fix null pointer dereference in blk_mq_clear_rq_mapping() Yu Kuai
2022-10-16 23:23 ` Jens Axboe
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