From: Yu Kuai yukuai3@huawei.com
[ Upstream commit 76dd298094f484c6250ebd076fa53287477b2328 ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- 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 887b8682eb69..fe840536e6ac 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -3028,8 +3028,11 @@ 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) {