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authorYu Kuai <yukuai3@huawei.com>2022-10-11 22:22:53 +0800
committerJens Axboe <axboe@kernel.dk>2022-10-16 17:22:51 -0600
commit76dd298094f484c6250ebd076fa53287477b2328 (patch)
tree4848bed6d3a876d7dd57e2ea65223cba8462348e /block/blk-mq.c
parent3bc429c1e2cf6fa830057c61ae93d483f270b8ff (diff)
blk-mq: fix null pointer dereference in blk_mq_clear_rq_mapping()
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> Link: https://lore.kernel.org/r/20221011142253.4015966-1-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-mq.c')
-rw-r--r--block/blk-mq.c7
1 files 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) {