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Date: Sat, 15 Oct 2022 11:58:41 +0800 From: Yu Kuai <yukuai1@...weicloud.com> To: Yu Kuai <yukuai1@...weicloud.com>, axboe@...nel.dk, ming.lei@...hat.com, hare@...e.de, john.garry@...wei.com Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org, yi.zhang@...wei.com, "yukuai (C)" <yukuai3@...wei.com> Subject: Re: [PATCH v2] blk-mq: fix null pointer dereference in blk_mq_clear_rq_mapping() Hi, Jens! 在 2022/10/11 22:22, Yu Kuai 写道: > From: Yu Kuai <yukuai3@...wei.com> > > 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@...wei.com> > Reviewed-by: John Garry <john.garry@...wei.com> > --- > Changes in v2: > - fix spelling mistakes > - add review tag > > block/blk-mq.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > Can you apply this patch? Thanks, Kuai > diff --git a/block/blk-mq.c b/block/blk-mq.c > index 8070b6c10e8d..33292c01875d 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -3112,8 +3112,11 @@ 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) { >
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