[PATCH v5.10] vhost-scsi: protect vq->log_used with vq->mutex

[PATCH v5.10] vhost-scsi: protect vq->log_used with vq->mutex

[Xinyu Zheng]

From: Dongli Zhang <dongli.zhang@oracle.com>

[ Upstream commit f591cf9fce724e5075cc67488c43c6e39e8cbe27 ]

The vhost-scsi completion path may access vq->log_base when vq->log_used is
already set to false.

    vhost-thread                       QEMU-thread

vhost_scsi_complete_cmd_work()
-> vhost_add_used()
   -> vhost_add_used_n()
      if (unlikely(vq->log_used))
                                      QEMU disables vq->log_used
                                      via VHOST_SET_VRING_ADDR.
                                      mutex_lock(&vq->mutex);
                                      vq->log_used = false now!
                                      mutex_unlock(&vq->mutex);

				      QEMU gfree(vq->log_base)
        log_used()
        -> log_write(vq->log_base)

Assuming the VMM is QEMU. The vq->log_base is from QEMU userpace and can be
reclaimed via gfree(). As a result, this causes invalid memory writes to
QEMU userspace.

The control queue path has the same issue.

CVE-2025-38074
Cc: stable@vger.kernel.org#5.10.x
Cc: gregkh@linuxfoundation.org
Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Mike Christie <michael.christie@oracle.com>
Message-Id: <20250403063028.16045-2-dongli.zhang@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Conflicts in drivers/vhost/scsi.c
  bacause vhost_scsi_complete_cmd_work() has been refactored. ]
Signed-off-by: Xinyu Zheng <zhengxinyu6@huawei.com>
---
 drivers/vhost/scsi.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index a23a65e7d828..fcde3752b4f1 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -579,8 +579,10 @@ static void vhost_scsi_complete_cmd_work(struct vhost_work *work)
 		ret = copy_to_iter(&v_rsp, sizeof(v_rsp), &iov_iter);
 		if (likely(ret == sizeof(v_rsp))) {
 			struct vhost_scsi_virtqueue *q;
-			vhost_add_used(cmd->tvc_vq, cmd->tvc_vq_desc, 0);
 			q = container_of(cmd->tvc_vq, struct vhost_scsi_virtqueue, vq);
+			mutex_lock(&q->vq.mutex);
+			vhost_add_used(cmd->tvc_vq, cmd->tvc_vq_desc, 0);
+			mutex_unlock(&q->vq.mutex);
 			vq = q - vs->vqs;
 			__set_bit(vq, signal);
 		} else
@@ -1193,8 +1195,11 @@ static void vhost_scsi_tmf_resp_work(struct vhost_work *work)
 	else
 		resp_code = VIRTIO_SCSI_S_FUNCTION_REJECTED;
 
+	mutex_lock(&tmf->svq->vq.mutex);
 	vhost_scsi_send_tmf_resp(tmf->vhost, &tmf->svq->vq, tmf->in_iovs,
 				 tmf->vq_desc, &tmf->resp_iov, resp_code);
+	mutex_unlock(&tmf->svq->vq.mutex);
+
 	vhost_scsi_release_tmf_res(tmf);
 }
 
-- 
2.34.1

Re: [PATCH v5.10] vhost-scsi: protect vq->log_used with vq->mutex

[Greg KH]

On Wed, Jul 02, 2025 at 08:29:45AM +0000, Xinyu Zheng wrote:
> From: Dongli Zhang <dongli.zhang@oracle.com>
> 
> [ Upstream commit f591cf9fce724e5075cc67488c43c6e39e8cbe27 ]
> 
> The vhost-scsi completion path may access vq->log_base when vq->log_used is
> already set to false.
> 
>     vhost-thread                       QEMU-thread
> 
> vhost_scsi_complete_cmd_work()
> -> vhost_add_used()
>    -> vhost_add_used_n()
>       if (unlikely(vq->log_used))
>                                       QEMU disables vq->log_used
>                                       via VHOST_SET_VRING_ADDR.
>                                       mutex_lock(&vq->mutex);
>                                       vq->log_used = false now!
>                                       mutex_unlock(&vq->mutex);
> 
> 				      QEMU gfree(vq->log_base)
>         log_used()
>         -> log_write(vq->log_base)
> 
> Assuming the VMM is QEMU. The vq->log_base is from QEMU userpace and can be
> reclaimed via gfree(). As a result, this causes invalid memory writes to
> QEMU userspace.
> 
> The control queue path has the same issue.
> 
> CVE-2025-38074

This is not needed.

> Cc: stable@vger.kernel.org#5.10.x

What about 5.15.y and 6.1.y?  We can't take a patch just for 5.10 as
that would cause regressions, right?

Please provide all relevant backports and I will be glad to queue them
up then.  I'll drop this from my queue for now, thanks.

greg k-h

Re: [PATCH v5.10] vhost-scsi: protect vq->log_used with vq->mutex

[zhengxinyu (E)]

On 7/10/2025 9:41 PM, Greg KH wrote:
> On Wed, Jul 02, 2025 at 08:29:45AM +0000, Xinyu Zheng wrote:
>> From: Dongli Zhang <dongli.zhang@oracle.com>
>>
>> [ Upstream commit f591cf9fce724e5075cc67488c43c6e39e8cbe27 ]
>>
>> The vhost-scsi completion path may access vq->log_base when vq->log_used is
>> already set to false.
>>
>>      vhost-thread                       QEMU-thread
>>
>> vhost_scsi_complete_cmd_work()
>> -> vhost_add_used()
>>     -> vhost_add_used_n()
>>        if (unlikely(vq->log_used))
>>                                        QEMU disables vq->log_used
>>                                        via VHOST_SET_VRING_ADDR.
>>                                        mutex_lock(&vq->mutex);
>>                                        vq->log_used = false now!
>>                                        mutex_unlock(&vq->mutex);
>>
>> 				      QEMU gfree(vq->log_base)
>>          log_used()
>>          -> log_write(vq->log_base)
>>
>> Assuming the VMM is QEMU. The vq->log_base is from QEMU userpace and can be
>> reclaimed via gfree(). As a result, this causes invalid memory writes to
>> QEMU userspace.
>>
>> The control queue path has the same issue.
>>
>> CVE-2025-38074
> 
> This is not needed.
> 
>> Cc: stable@vger.kernel.org#5.10.x
> 
> What about 5.15.y and 6.1.y?  We can't take a patch just for 5.10 as
> that would cause regressions, right?
> 
> Please provide all relevant backports and I will be glad to queue them
> up then.  I'll drop this from my queue for now, thanks.
> 
> greg k-h

Sorry for forgetting the 5.15.y and 6.1.y patches. I will resend it as 
soon as possible. Thanks for pointing out my patch format error.

Xinyu Zheng