blk-mq: add bounds check on tag-to-rq conversion

We need to check for a valid index before accessing the array
element to avoid accessing invalid memory regions.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Modified by Jens to drop the unlikely(), and make the fall through
path be having a valid tag.

Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 5667f59c277c5052dca7a4e4e4d643d8c06cfa5f..261b6feddae6a30b5ebb6e085ba9fd32bb0e6477 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -544,7 +544,10 @@ EXPORT_SYMBOL(blk_mq_abort_requeue_list);
 
 struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag)
 {
-       return tags->rqs[tag];
+       if (tag < tags->nr_tags)
+               return tags->rqs[tag];
+
+       return NULL;
 }
 EXPORT_SYMBOL(blk_mq_tag_to_rq);