Re: [PATCH] block: fix use-after-free of q->q_usage_counter

[Greg KH]

On Thu, Sep 21, 2023 at 11:20:12AM -0700, Saranya Muruganandam wrote:
> From: Ming Lei <ming.lei@xxxxxxxxxx>
> 
> commit d36a9ea5e7766961e753ee38d4c331bbe6ef659b upstream.
> 
> For blk-mq, queue release handler is usually called after
> blk_mq_freeze_queue_wait() returns. However, the
> q_usage_counter->release() handler may not be run yet at that time, so
> this can cause a use-after-free.
> 
> Fix the issue by moving percpu_ref_exit() into blk_free_queue_rcu().
> Since ->release() is called with rcu read lock held, it is agreed that
> the race should be covered in caller per discussion from the two links.
> 
> Backport-notes: Not a clean cherry-pick since a lot has changed,
> however essentially the same fix.
> 
> Reported-by: Zhang Wensheng <zhangwensheng@xxxxxxxxxxxxxxx>
> Reported-by: Zhong Jinghua <zhongjinghua@xxxxxxxxxx>
> Link: https://lore.kernel.org/linux-block/Y5prfOjyyjQKUrtH@T590/T/#u
> Link: https://lore.kernel.org/lkml/Y4%2FmzMd4evRg9yDi@fedora/
> Cc: Hillf Danton <hdanton@xxxxxxxx>
> Cc: Yu Kuai <yukuai3@xxxxxxxxxx>
> Cc: Dennis Zhou <dennis@xxxxxxxxxx>
> Fixes: 2b0d3d3e4fcf ("percpu_ref: reduce memory footprint of percpu_ref in fast path")
> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
> Link: https://lore.kernel.org/r/20221215021629.74870-1-ming.lei@xxxxxxxxxx
> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
> Signed-off-by: Saranya Muruganandam <saranyamohan@xxxxxxxxxx>
> ---
>  block/blk-core.c  | 2 --
>  block/blk-sysfs.c | 2 ++
>  2 files changed, 2 insertions(+), 2 deletions(-)

What stable kernel(s) are you expecting this backport to be applied to?

thanks,

greg "not a mind reader" k-h