Messages in this thread Patch in this message | | | From | Yu Kuai <> | Subject | [PATCH v2] blk-mq: fix null pointer dereference in blk_mq_clear_rq_mapping() | Date | Tue, 11 Oct 2022 22:22:53 +0800 |
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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
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