[PATCH] vsock: lookup and setup guest_cid inside vhost_vsock_lock

[Gao feng]

Multi vsocks may setup the same cid at the same time.

Signed-off-by: Gao feng 
---
 drivers/vhost/vsock.c | 25 +
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index e3b30ea..a08332b 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -50,11 +50,10 @@ static u32 vhost_transport_get_local_cid(void)
return VHOST_VSOCK_DEFAULT_HOST_CID;
 }
 
-static struct vhost_vsock *vhost_vsock_get(u32 guest_cid)
+static struct vhost_vsock *__vhost_vsock_get(u32 guest_cid)
 {
struct vhost_vsock *vsock;
 
-   spin_lock_bh(_vsock_lock);
list_for_each_entry(vsock, _vsock_list, list) {
u32 other_cid = vsock->guest_cid;
 
@@ -63,15 +62,24 @@ static struct vhost_vsock *vhost_vsock_get(u32 guest_cid)
continue;
 
if (other_cid == guest_cid) {
-   spin_unlock_bh(_vsock_lock);
return vsock;
}
}
-   spin_unlock_bh(_vsock_lock);
 
return NULL;
 }
 
+static struct vhost_vsock *vhost_vsock_get(u32 guest_cid)
+{
+   struct vhost_vsock *vsock;
+
+   spin_lock_bh(_vsock_lock);
+   vsock = __vhost_vsock_get(guest_cid);
+   spin_unlock_bh(_vsock_lock);
+
+   return vsock;
+}
+
 static void
 vhost_transport_do_send_pkt(struct vhost_vsock *vsock,
struct vhost_virtqueue *vq)
@@ -562,11 +570,12 @@ static int vhost_vsock_set_cid(struct vhost_vsock *vsock, 
u64 guest_cid)
return -EINVAL;
 
/* Refuse if CID is already in use */
-   other = vhost_vsock_get(guest_cid);
-   if (other && other != vsock)
-   return -EADDRINUSE;
-
spin_lock_bh(_vsock_lock);
+   other = __vhost_vsock_get(guest_cid);
+   if (other && other != vsock) {
+   spin_unlock_bh(_vsock_lock);
+   return -EADDRINUSE;
+   }
vsock->guest_cid = guest_cid;
spin_unlock_bh(_vsock_lock);
 
-- 
2.5.5

Re: [PATCH] vsock: lookup and setup guest_cid inside vhost_vsock_lock

[Stefan Hajnoczi]

On Wed, Dec 14, 2016 at 07:24:36PM +0800, Gao feng wrote:
> Multi vsocks may setup the same cid at the same time.
> 
> Signed-off-by: Gao feng 
> ---
>  drivers/vhost/vsock.c | 25 +
>  1 file changed, 17 insertions(+), 8 deletions(-)

Good catch, a classic time-of-check-to-time-of-use race condition.

Reviewed-by: Stefan Hajnoczi 


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