virtio-blk: Avoid use-after-free on suspend/resume

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().

Fixes: 4e0400525691 ("virtio-blk: support polling I/O")
Cc: "Suwan Kim" <suwan.kim027@gmail.com>
Signed-off-by: Shigeru Yoshida <syoshida@redhat.com>
Message-Id: <20220810160948.959781-1-syoshida@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 6fc7850..d756423 100644 (file)
--- 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,