netdev - [PATCH] vhost/vsock: always initialize seqpacket

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Message-ID: <bcc17a060d93b198d8a17a9b87b593f41337ee28.1715785488.git.mst@redhat.com>
Date: Wed, 15 May 2024 11:05:43 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: syzbot+6c21aeb59d0e82eb2782@...kaller.appspotmail.com,
	Jeongjun Park <aha310510@...il.com>,
	Arseny Krasnov <arseny.krasnov@...persky.com>,
	"David S . Miller" <davem@...emloft.net>,
	Stefan Hajnoczi <stefanha@...hat.com>,
	Stefano Garzarella <sgarzare@...hat.com>,
	Jason Wang <jasowang@...hat.com>,
	Eugenio Pérez <eperezma@...hat.com>,
	kvm@...r.kernel.org, virtualization@...ts.linux.dev,
	netdev@...r.kernel.org
Subject: [PATCH] vhost/vsock: always initialize seqpacket_allow

There are two issues around seqpacket_allow:
1. seqpacket_allow is not initialized when socket is
   created. Thus if features are never set, it will be
   read uninitialized.
2. if VIRTIO_VSOCK_F_SEQPACKET is set and then cleared,
   then seqpacket_allow will not be cleared appropriately
   (existing apps I know about don't usually do this but
    it's legal and there's no way to be sure no one relies
    on this).

To fix:
	- initialize seqpacket_allow after allocation
	- set it unconditionally in set_features

Reported-by: syzbot+6c21aeb59d0e82eb2782@...kaller.appspotmail.com
Reported-by: Jeongjun Park <aha310510@...il.com>
Fixes: ced7b713711f ("vhost/vsock: support SEQPACKET for transport").
Cc: Arseny Krasnov <arseny.krasnov@...persky.com>
Cc: David S. Miller <davem@...emloft.net>
Cc: Stefan Hajnoczi <stefanha@...hat.com>
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
Acked-by: Arseniy Krasnov <avkrasnov@...utedevices.com>
Tested-by: Arseniy Krasnov <avkrasnov@...utedevices.com>

---


Reposting now it's been tested.

 drivers/vhost/vsock.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index ec20ecff85c7..bf664ec9341b 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -667,6 +667,7 @@ static int vhost_vsock_dev_open(struct inode *inode, struct file *file)
 	}
 
 	vsock->guest_cid = 0; /* no CID assigned yet */
+	vsock->seqpacket_allow = false;
 
 	atomic_set(&vsock->queued_replies, 0);
 
@@ -810,8 +811,7 @@ static int vhost_vsock_set_features(struct vhost_vsock *vsock, u64 features)
 			goto err;
 	}
 
-	if (features & (1ULL << VIRTIO_VSOCK_F_SEQPACKET))
-		vsock->seqpacket_allow = true;
+	vsock->seqpacket_allow = features & (1ULL << VIRTIO_VSOCK_F_SEQPACKET);
 
 	for (i = 0; i < ARRAY_SIZE(vsock->vqs); i++) {
 		vq = &vsock->vqs[i];
-- 
MST