lkml.org 
[lkml]   [2022]   [Jul]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [RFC] block: Add a NULL check in blk_mq_free_rqs()
From
On 7/17/22 03:22, Gautam Menghani wrote:
> Syzbot reported a general protection fault in the function
> blk_mq_clear_rq_mapping() in the file block/blk-mq.c.
> The issue is that the variable drv_tags is NULL, and this
> originates from the struct blk_mq_tag_set. The dashboard link for this
> issue is :
> syzkaller.appspot.com/bug?id=c3ce4caa4fc58c156d4903984131cdfa38eee354
>
> This patch fixes the above bug, but there is another syzbot bug which is
> related to this and getting triggered after the call to
> blk_mq_clear_rq_mapping(). As a result, I cannot determine if the issue
> is really solved. The link to other issue:
> syzkaller.appspot.com/bug?id=7643cea70f1d0ce15f5f4bc39488918837ad4233
>
> Please provide feedback/suggestions on the same.
>
> Signed-off-by: Gautam Menghani <gautammenghani201@gmail.com>
> ---
> block/blk-mq.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 93d9d60980fb..c1dd1b78b95c 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -3092,7 +3092,8 @@ void blk_mq_free_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags,
> }
> }
>
> - blk_mq_clear_rq_mapping(drv_tags, tags);
> + if (drv_tags)
> + blk_mq_clear_rq_mapping(drv_tags, tags);
>
> while (!list_empty(&tags->page_list)) {
> page = list_first_entry(&tags->page_list, struct page, lru);

I don't see how drv_tags could be NULL without triggering a race
condition. Please take a look at the nbd driver to see whether the root
cause is perhaps in that driver instead of in the block layer core.

Thanks,

Bart.

\
 
 \ /
  Last update: 2022-07-17 16:50    [W:0.167 / U:0.132 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site