Re: [Qemu-devel] [Qemu-trivial] [PATCH v6 03/10] virtio-blk: fix reference a pointer which might be freed

[Michael Tokarev]

14.08.2014 11:29, zhanghailiang wrote:
> In function virtio_blk_handle_request, it may freed memory pointed by req,
> So do not access member of req after calling this function.
> 
> Reviewed-by: Stefan Hajnoczi <stefa...@redhat.com>
> Signed-off-by: zhanghailiang <zhang.zhanghaili...@huawei.com>
> ---
>  hw/block/virtio-blk.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
> index c241c50..54a853a 100644
> --- a/hw/block/virtio-blk.c
> +++ b/hw/block/virtio-blk.c
> @@ -458,7 +458,7 @@ static void virtio_blk_handle_output(VirtIODevice *vdev, 
> VirtQueue *vq)
>  static void virtio_blk_dma_restart_bh(void *opaque)
>  {
>      VirtIOBlock *s = opaque;
> -    VirtIOBlockReq *req = s->rq;
> +    VirtIOBlockReq *req = s->rq, *next = NULL;
>      MultiReqBuffer mrb = {
>          .num_writes = 0,
>      };
> @@ -469,8 +469,9 @@ static void virtio_blk_dma_restart_bh(void *opaque)
>      s->rq = NULL;
>  
>      while (req) {
> +        next = req->next;
>          virtio_blk_handle_request(req, &mrb);
> -        req = req->next;
> +        req = next;
>      }
>  
>      virtio_submit_multiwrite(s->bs, &mrb);

So, finally, I've applied this patch:

--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -469,8 +469,9 @@ static void virtio_blk_dma_restart_bh(void *opaque)
     s->rq = NULL;

     while (req) {
+        VirtIOBlockReq *next = req->next;
         virtio_blk_handle_request(req, &mrb);
-        req = req->next;
+        req = next;
     }

     virtio_submit_multiwrite(s->bs, &mrb);

and dropped Stefan's Reviewed-by on the way ;)

This is a bugfix after all ;)

Thanks,

/mjt