linux-kernel - RE: [PATCH] blk-mq: use after free when freeing tag sets

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Message-ID: <B58D82457FDA0744A320A2FC5AC253B93CD22D1C@fmsmsx104.amr.corp.intel.com>
Date:	Fri, 16 Oct 2015 18:00:33 +0000
From:	"Busch, Keith" <keith.busch@...el.com>
To:	Sasha Levin <sasha.levin@...cle.com>,
	"axboe@...nel.dk" <axboe@...nel.dk>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] blk-mq: use after free when freeing tag sets

Oh, the same fix was applied from another developer:

https://git.kernel.org/cgit/linux/kernel/git/axboe/linux-block.git/commit/?h=for-linus&id=f42d79ab67322e51b92dd7aa965e310c71352a64

Yours came first, though I just missed it.


> On 10/02/2015 09:40 PM, Sasha Levin wrote:
> > Commit f26cdc853 ("blk-mq: Shared tag enhancements") has introduced a use after
> > free where it tried to free the cpumask var out of the tag set but the tag set
> > was already freed by blk_mq_free_rq_map().
> >
> > Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
> > ---
> >  block/blk-mq-tag.c |    1 +
> >  block/blk-mq.c     |    7 ++-----
> >  2 files changed, 3 insertions(+), 5 deletions(-)
> >
> > diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
> > index f6020c6..c03eeb8 100644
> > --- a/block/blk-mq-tag.c
> > +++ b/block/blk-mq-tag.c
> > @@ -628,6 +628,7 @@ void blk_mq_free_tags(struct blk_mq_tags *tags)
> >  {
> >  	bt_free(&tags->bitmap_tags);
> >  	bt_free(&tags->breserved_tags);
> > +	free_cpumask_var(tags->cpumask);
> >  	kfree(tags);
> >  }
> >
> > diff --git a/block/blk-mq.c b/block/blk-mq.c
> > index 5692c15..197a615 100644
> > --- a/block/blk-mq.c
> > +++ b/block/blk-mq.c
> > @@ -2270,12 +2270,9 @@ void blk_mq_free_tag_set(struct blk_mq_tag_set *set)
> >  {
> >  	int i;
> >
> > -	for (i = 0; i < set->nr_hw_queues; i++) {
> > -		if (set->tags[i]) {
> > +	for (i = 0; i < set->nr_hw_queues; i++)
> > +		if (set->tags[i])
> >  			blk_mq_free_rq_map(set, set->tags[i], i);
> > -			free_cpumask_var(set->tags[i]->cpumask);
> > -		}
> > -	}
> >
> >  	kfree(set->tags);
> >  	set->tags = NULL;
> >

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