Re: [PATCH 3.18.y 4.4.y 4.9.y] block: blk_init_allocated_queue() set q->fq as NULL in the fail case

[Alessio Balsini]

Oops, thanks!

On Thu, Aug 8, 2019 at 2:00 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Thu, Aug 08, 2019 at 03:28:19AM +0100, Alessio Balsini wrote:
> > From: xiao jin <jin.xiao@xxxxxxxxx>
> >
> > commit 54648cf1ec2d7f4b6a71767799c45676a138ca24 upstream.
> >
> > We find the memory use-after-free issue in __blk_drain_queue()
> > on the kernel 4.14. After read the latest kernel 4.18-rc6 we
> > think it has the same problem.
> >
> > Memory is allocated for q->fq in the blk_init_allocated_queue().
> > If the elevator init function called with error return, it will
> > run into the fail case to free the q->fq.
> >
> > Then the __blk_drain_queue() uses the same memory after the free
> > of the q->fq, it will lead to the unpredictable event.
> >
> > The patch is to set q->fq as NULL in the fail case of
> > blk_init_allocated_queue().
> >
> > Fixes: commit 7c94e1c157a2 ("block: introduce blk_flush_queue to drive flush machinery")
> > Cc: <stable@xxxxxxxxxxxxxxx>
> > Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>
> > Reviewed-by: Bart Van Assche <bart.vanassche@xxxxxxx>
> > Signed-off-by: xiao jin <jin.xiao@xxxxxxxxx>
> > Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
> > Signed-off-by: Alessio Balsini <balsini@xxxxxxxxxxx>
> > ---
> >  block/blk-core.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/block/blk-core.c b/block/blk-core.c
> > index 50d77c90070d..7662f97dded6 100644
> > --- a/block/blk-core.c
> > +++ b/block/blk-core.c
> > @@ -870,6 +870,7 @@ blk_init_allocated_queue(struct request_queue *q, request_fn_proc *rfn,
> >
> >  fail:
> >       blk_free_flush_queue(q->fq);
> > +     q->fq = NULL;
> >       return NULL;
> >  }
> >  EXPORT_SYMBOL(blk_init_allocated_queue);
> > --
> > 2.22.0.770.g0f2c4a37fd-goog
> >
>
> Guenter sent this backport a day before you did, so I took his version
> and added your s-o-b to it.
>
> thanks,
>
> greg k-h