linux-kernel - [PATCH AUTOSEL 6.6 14/21] vhost-scsi: protect vq->log

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Message-Id: <20250429235233.537828-14-sashal@kernel.org>
Date: Tue, 29 Apr 2025 19:52:26 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Dongli Zhang <dongli.zhang@...cle.com>,
	Jason Wang <jasowang@...hat.com>,
	Mike Christie <michael.christie@...cle.com>,
	"Michael S . Tsirkin" <mst@...hat.com>,
	Sasha Levin <sashal@...nel.org>,
	virtualization@...ts.linux.dev,
	kvm@...r.kernel.org,
	netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 6.6 14/21] vhost-scsi: protect vq->log_used with vq->mutex

From: Dongli Zhang <dongli.zhang@...cle.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.

Signed-off-by: Dongli Zhang <dongli.zhang@...cle.com>
Acked-by: Jason Wang <jasowang@...hat.com>
Reviewed-by: Mike Christie <michael.christie@...cle.com>
Message-Id: <20250403063028.16045-2-dongli.zhang@...cle.com>
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/vhost/scsi.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 8d8a22504d71f..724dd69c86489 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -560,6 +560,9 @@ static void vhost_scsi_complete_cmd_work(struct vhost_work *work)
 	int ret;
 
 	llnode = llist_del_all(&svq->completion_list);
+
+	mutex_lock(&svq->vq.mutex);
+
 	llist_for_each_entry_safe(cmd, t, llnode, tvc_completion_list) {
 		se_cmd = &cmd->tvc_se_cmd;
 
@@ -593,6 +596,8 @@ static void vhost_scsi_complete_cmd_work(struct vhost_work *work)
 		vhost_scsi_release_cmd_res(se_cmd);
 	}
 
+	mutex_unlock(&svq->vq.mutex);
+
 	if (signal)
 		vhost_signal(&svq->vs->dev, &svq->vq);
 }
@@ -1301,8 +1306,11 @@ static void vhost_scsi_tmf_resp_work(struct vhost_work *work)
 		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);
 }
 
-- 
2.39.5