Re: [PATCH] virtio-blk: Avoid use-after-free on suspend/resume

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Aug 10, 2022 at 08:45:56PM +0900, Shigeru Yoshida wrote:
> ping?
> 
> On Sun, 31 Jul 2022 16:09:51 +0900, Shigeru Yoshida wrote:
> > hctx->user_data is set to vq in virtblk_init_hctx().  However, vq is
> > freed on suspend and reallocated on resume.  So, hctx->user_data is
> > invalid after resume, and it will cause use-after-free accessing which
> > will result in the kernel crash something like below:
> > 
> > [   22.428391] Call Trace:
> > [   22.428899]  <TASK>
> > [   22.429339]  virtqueue_add_split+0x3eb/0x620
> > [   22.430035]  ? __blk_mq_alloc_requests+0x17f/0x2d0
> > [   22.430789]  ? kvm_clock_get_cycles+0x14/0x30
> > [   22.431496]  virtqueue_add_sgs+0xad/0xd0
> > [   22.432108]  virtblk_add_req+0xe8/0x150
> > [   22.432692]  virtio_queue_rqs+0xeb/0x210
> > [   22.433330]  blk_mq_flush_plug_list+0x1b8/0x280
> > [   22.434059]  __blk_flush_plug+0xe1/0x140
> > [   22.434853]  blk_finish_plug+0x20/0x40
> > [   22.435512]  read_pages+0x20a/0x2e0
> > [   22.436063]  ? folio_add_lru+0x62/0xa0
> > [   22.436652]  page_cache_ra_unbounded+0x112/0x160
> > [   22.437365]  filemap_get_pages+0xe1/0x5b0
> > [   22.437964]  ? context_to_sid+0x70/0x100
> > [   22.438580]  ? sidtab_context_to_sid+0x32/0x400
> > [   22.439979]  filemap_read+0xcd/0x3d0
> > [   22.440917]  xfs_file_buffered_read+0x4a/0xc0
> > [   22.441984]  xfs_file_read_iter+0x65/0xd0
> > [   22.442970]  __kernel_read+0x160/0x2e0
> > [   22.443921]  bprm_execve+0x21b/0x640
> > [   22.444809]  do_execveat_common.isra.0+0x1a8/0x220
> > [   22.446008]  __x64_sys_execve+0x2d/0x40
> > [   22.446920]  do_syscall_64+0x37/0x90
> > [   22.447773]  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> > 
> > This patch fixes this issue by getting vq from vblk, and removes
> > virtblk_init_hctx().
> > 
> > Signed-off-by: Shigeru Yoshida <shigeru.yoshida@gmail.com>

Fixes: 4e0400525691 ("virtio-blk: support polling I/O")
Cc: "Suwan Kim" <suwan.kim027@gmail.com>

I assume?

> > ---
> >  drivers/block/virtio_blk.c | 24 ++++++++++--------------
> >  1 file changed, 10 insertions(+), 14 deletions(-)
> > 
> > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> > index 6fc7850c2b0a..d756423e0059 100644
> > --- a/drivers/block/virtio_blk.c
> > +++ b/drivers/block/virtio_blk.c
> > @@ -101,6 +101,14 @@ static inline blk_status_t virtblk_result(struct virtblk_req *vbr)
> >  	}
> >  }
> >  
> > +static inline struct virtio_blk_vq *get_virtio_blk_vq(struct blk_mq_hw_ctx *hctx)
> > +{
> > +	struct virtio_blk *vblk = hctx->queue->queuedata;
> > +	struct virtio_blk_vq *vq = &vblk->vqs[hctx->queue_num];
> > +
> > +	return vq;
> > +}
> > +
> >  static int virtblk_add_req(struct virtqueue *vq, struct virtblk_req *vbr)
> >  {
> >  	struct scatterlist hdr, status, *sgs[3];
> > @@ -416,7 +424,7 @@ static void virtio_queue_rqs(struct request **rqlist)
> >  	struct request *requeue_list = NULL;
> >  
> >  	rq_list_for_each_safe(rqlist, req, next) {
> > -		struct virtio_blk_vq *vq = req->mq_hctx->driver_data;
> > +		struct virtio_blk_vq *vq = get_virtio_blk_vq(req->mq_hctx);
> >  		bool kick;
> >  
> >  		if (!virtblk_prep_rq_batch(req)) {
> > @@ -837,7 +845,7 @@ static void virtblk_complete_batch(struct io_comp_batch *iob)
> >  static int virtblk_poll(struct blk_mq_hw_ctx *hctx, struct io_comp_batch *iob)
> >  {
> >  	struct virtio_blk *vblk = hctx->queue->queuedata;
> > -	struct virtio_blk_vq *vq = hctx->driver_data;
> > +	struct virtio_blk_vq *vq = get_virtio_blk_vq(hctx);
> >  	struct virtblk_req *vbr;
> >  	unsigned long flags;
> >  	unsigned int len;
> > @@ -862,22 +870,10 @@ static int virtblk_poll(struct blk_mq_hw_ctx *hctx, struct io_comp_batch *iob)
> >  	return found;
> >  }
> >  
> > -static int virtblk_init_hctx(struct blk_mq_hw_ctx *hctx, void *data,
> > -			  unsigned int hctx_idx)
> > -{
> > -	struct virtio_blk *vblk = data;
> > -	struct virtio_blk_vq *vq = &vblk->vqs[hctx_idx];
> > -
> > -	WARN_ON(vblk->tag_set.tags[hctx_idx] != hctx->tags);
> > -	hctx->driver_data = vq;
> > -	return 0;
> > -}
> > -
> >  static const struct blk_mq_ops virtio_mq_ops = {
> >  	.queue_rq	= virtio_queue_rq,
> >  	.queue_rqs	= virtio_queue_rqs,
> >  	.commit_rqs	= virtio_commit_rqs,
> > -	.init_hctx	= virtblk_init_hctx,
> >  	.complete	= virtblk_request_done,
> >  	.map_queues	= virtblk_map_queues,
> >  	.poll		= virtblk_poll,
> > -- 
> > 2.37.1
> >