[PATCH for 3.4] virtio-scsi: fix TMF use-after-free

[PATCH for 3.4] virtio-scsi: fix TMF use-after-free

[Paolo Bonzini]

Fix a race in TMF path, where cmd may have been already freed
by virtscsi_complete_free after waking up from the completion.

Cc: James Bottomley <JBottomley@parallels.com>
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 drivers/scsi/virtio_scsi.c |   24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
index efccd72..1b38431 100644
--- a/drivers/scsi/virtio_scsi.c
+++ b/drivers/scsi/virtio_scsi.c
@@ -175,7 +175,8 @@ static void virtscsi_complete_free(void *buf)
 
 	if (cmd->comp)
 		complete_all(cmd->comp);
-	mempool_free(cmd, virtscsi_cmd_pool);
+	else
+		mempool_free(cmd, virtscsi_cmd_pool);
 }
 
 static void virtscsi_ctrl_done(struct virtqueue *vq)
@@ -311,21 +312,22 @@ out:
 static int virtscsi_tmf(struct virtio_scsi *vscsi, struct virtio_scsi_cmd *cmd)
 {
 	DECLARE_COMPLETION_ONSTACK(comp);
-	int ret;
+	int ret = FAILED;
 
 	cmd->comp = &comp;
-	ret = virtscsi_kick_cmd(vscsi, vscsi->ctrl_vq, cmd,
-			       sizeof cmd->req.tmf, sizeof cmd->resp.tmf,
-			       GFP_NOIO);
-	if (ret < 0)
-		return FAILED;
+	if (virtscsi_kick_cmd(vscsi, vscsi->ctrl_vq, cmd,
+			      sizeof cmd->req.tmf, sizeof cmd->resp.tmf,
+			      GFP_NOIO) < 0)
+		goto out;
 
 	wait_for_completion(&comp);
-	if (cmd->resp.tmf.response != VIRTIO_SCSI_S_OK &&
-	    cmd->resp.tmf.response != VIRTIO_SCSI_S_FUNCTION_SUCCEEDED)
-		return FAILED;
+	if (cmd->resp.tmf.response == VIRTIO_SCSI_S_OK ||
+	    cmd->resp.tmf.response == VIRTIO_SCSI_S_FUNCTION_SUCCEEDED)
+		ret = SUCCESS;
 
-	return SUCCESS;
+out:
+	mempool_free(cmd, virtscsi_cmd_pool);
+	return ret;
 }
 
 static int virtscsi_device_reset(struct scsi_cmnd *sc)
-- 
1.7.9.3

Re: [PATCH for 3.4] virtio-scsi: fix TMF use-after-free

[Zhi Yong Wu]

On Wed, Apr 18, 2012 at 9:46 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:
> Fix a race in TMF path, where cmd may have been already freed
> by virtscsi_complete_free after waking up from the completion.
>
> Cc: James Bottomley <JBottomley@parallels.com>
> Cc: linux-scsi@vger.kernel.org
> Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  drivers/scsi/virtio_scsi.c |   24 +++++++++++++-----------
>  1 file changed, 13 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
> index efccd72..1b38431 100644
> --- a/drivers/scsi/virtio_scsi.c
> +++ b/drivers/scsi/virtio_scsi.c
> @@ -175,7 +175,8 @@ static void virtscsi_complete_free(void *buf)
>
>        if (cmd->comp)
>                complete_all(cmd->comp);
> -       mempool_free(cmd, virtscsi_cmd_pool);
> +       else
> +               mempool_free(cmd, virtscsi_cmd_pool);
good catch
>  }
>
>  static void virtscsi_ctrl_done(struct virtqueue *vq)
> @@ -311,21 +312,22 @@ out:
>  static int virtscsi_tmf(struct virtio_scsi *vscsi, struct virtio_scsi_cmd *cmd)
>  {
>        DECLARE_COMPLETION_ONSTACK(comp);
> -       int ret;
> +       int ret = FAILED;
>
>        cmd->comp = &comp;
> -       ret = virtscsi_kick_cmd(vscsi, vscsi->ctrl_vq, cmd,
> -                              sizeof cmd->req.tmf, sizeof cmd->resp.tmf,
> -                              GFP_NOIO);
> -       if (ret < 0)
> -               return FAILED;
> +       if (virtscsi_kick_cmd(vscsi, vscsi->ctrl_vq, cmd,
> +                             sizeof cmd->req.tmf, sizeof cmd->resp.tmf,
> +                             GFP_NOIO) < 0)
> +               goto out;
>
>        wait_for_completion(&comp);
> -       if (cmd->resp.tmf.response != VIRTIO_SCSI_S_OK &&
> -           cmd->resp.tmf.response != VIRTIO_SCSI_S_FUNCTION_SUCCEEDED)
> -               return FAILED;
> +       if (cmd->resp.tmf.response == VIRTIO_SCSI_S_OK ||
> +           cmd->resp.tmf.response == VIRTIO_SCSI_S_FUNCTION_SUCCEEDED)
> +               ret = SUCCESS;
>
> -       return SUCCESS;
> +out:
> +       mempool_free(cmd, virtscsi_cmd_pool);
> +       return ret;
>  }
>
>  static int virtscsi_device_reset(struct scsi_cmnd *sc)
> --
> 1.7.9.3

Reviewed-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
>
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-- 
Regards,

Zhi Yong Wu

Re: [PATCH for 3.4] virtio-scsi: fix TMF use-after-free

[James Bottomley]

On Wed, 2012-04-18 at 15:46 +0200, Paolo Bonzini wrote:
> Fix a race in TMF path, where cmd may have been already freed
> by virtscsi_complete_free after waking up from the completion.

There's no may about this; the command will be freed long before the
completion waiter is awoken.  The description could be clearer.

The problem is a use after free in virtscsi_tmf because the
virtio_scsi_command is freed before the completion returns.

The fix is to make callers specifying a completion responsible for
freeing the command in all cases.

James

> Cc: James Bottomley <JBottomley@parallels.com>
> Cc: linux-scsi@vger.kernel.org
> Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  drivers/scsi/virtio_scsi.c |   24 +++++++++++++-----------
>  1 file changed, 13 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
> index efccd72..1b38431 100644
> --- a/drivers/scsi/virtio_scsi.c
> +++ b/drivers/scsi/virtio_scsi.c
> @@ -175,7 +175,8 @@ static void virtscsi_complete_free(void *buf)
>  
>  	if (cmd->comp)
>  		complete_all(cmd->comp);
> -	mempool_free(cmd, virtscsi_cmd_pool);
> +	else
> +		mempool_free(cmd, virtscsi_cmd_pool);
>  }
>  
>  static void virtscsi_ctrl_done(struct virtqueue *vq)
> @@ -311,21 +312,22 @@ out:
>  static int virtscsi_tmf(struct virtio_scsi *vscsi, struct virtio_scsi_cmd *cmd)
>  {
>  	DECLARE_COMPLETION_ONSTACK(comp);
> -	int ret;
> +	int ret = FAILED;
>  
>  	cmd->comp = &comp;
> -	ret = virtscsi_kick_cmd(vscsi, vscsi->ctrl_vq, cmd,
> -			       sizeof cmd->req.tmf, sizeof cmd->resp.tmf,
> -			       GFP_NOIO);
> -	if (ret < 0)
> -		return FAILED;
> +	if (virtscsi_kick_cmd(vscsi, vscsi->ctrl_vq, cmd,
> +			      sizeof cmd->req.tmf, sizeof cmd->resp.tmf,
> +			      GFP_NOIO) < 0)
> +		goto out;
>  
>  	wait_for_completion(&comp);
> -	if (cmd->resp.tmf.response != VIRTIO_SCSI_S_OK &&
> -	    cmd->resp.tmf.response != VIRTIO_SCSI_S_FUNCTION_SUCCEEDED)
> -		return FAILED;
> +	if (cmd->resp.tmf.response == VIRTIO_SCSI_S_OK ||
> +	    cmd->resp.tmf.response == VIRTIO_SCSI_S_FUNCTION_SUCCEEDED)
> +		ret = SUCCESS;
>  
> -	return SUCCESS;
> +out:
> +	mempool_free(cmd, virtscsi_cmd_pool);
> +	return ret;
>  }
>  
>  static int virtscsi_device_reset(struct scsi_cmnd *sc)

Re: [PATCH for 3.4] virtio-scsi: fix TMF use-after-free

[Paolo Bonzini]

Il 18/04/2012 16:09, James Bottomley ha scritto:
>> > Fix a race in TMF path, where cmd may have been already freed
>> > by virtscsi_complete_free after waking up from the completion.
> There's no may about this; the command will be freed long before the
> completion waiter is awoken.  The description could be clearer.
> 
> The problem is a use after free in virtscsi_tmf because the
> virtio_scsi_command is freed before the completion returns.
> 
> The fix is to make callers specifying a completion responsible for
> freeing the command in all cases.

I don't see this in the pull request, were you waiting for v2 with a
better commit message?

Paolo

Re: [PATCH for 3.4] virtio-scsi: fix TMF use-after-free

[James Bottomley]

On Tue, 2012-05-01 at 10:09 +0200, Paolo Bonzini wrote:
> Il 18/04/2012 16:09, James Bottomley ha scritto:
> >> > Fix a race in TMF path, where cmd may have been already freed
> >> > by virtscsi_complete_free after waking up from the completion.
> > There's no may about this; the command will be freed long before the
> > completion waiter is awoken.  The description could be clearer.
> > 
> > The problem is a use after free in virtscsi_tmf because the
> > virtio_scsi_command is freed before the completion returns.
> > 
> > The fix is to make callers specifying a completion responsible for
> > freeing the command in all cases.
> 
> I don't see this in the pull request, were you waiting for v2 with a
> better commit message?

That would be because you didn't reply.  I was expecting either a
comment or a rewording of the change log.  My inbox works by threads
rising to the top and completed ones going into the patch queue.  If
no-one replys to a thread expecting one, it just gets lost.

James