On 03/16/2016 12:03 AM, Hannes Reinecke wrote:
On 03/15/2016 08:01 PM, Jens Axboe wrote:
On 03/15/2016 01:21 AM, Hannes Reinecke wrote:
We need to check for a valid index before accessing the array
element to avoid accessing invalid memory regions.
Signed-off-by: Hannes Reinecke <hare@xxxxxxxx>
---
block/blk-mq.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 56c0a72..4ea87d5 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -544,6 +544,8 @@ EXPORT_SYMBOL(blk_mq_abort_requeue_list);
struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags,
unsigned int tag)
{
+ if (unlikely(tag >= tags->nr_tags))
+ return NULL;
return tags->rqs[tag];
}
EXPORT_SYMBOL(blk_mq_tag_to_rq);
I like adding the check, but I think we should kill the unlikely and
just make it:
if (tag < tags->nr_tags)
return tags->rqs[tag];
return NULL;
instead. I'll apply it as such.
yeah, I had a discussion about the viability of the 'unlikely' flag
given modern compilers. No consensus was reached, so I left it in.
Removing it is fine by me, too.
The hope is that when you flip the case you check for, the fast and
expected path is in line and doesn't require a jump.
--
Jens Axboe
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