vsock_connect() expects that the socket could already be in the
TCP_ESTABLISHED state when the connecting task wakes up with a signal
pending. If this happens the socket will be in the connected table, and
it is not removed when the socket state is reset. In this situation it's
common for the process to retry connect(), and if the connection is
successful the socket will be added to the connected table a second
time, corrupting the list.

Prevent this by calling vsock_remove_connected() if a signal is received
while waiting for a connection. This is harmless if the socket is not in
the connected table, and if it is in the table then removing it will
prevent list corruption from a double add.

Note for backporting: this patch requires d5afa82c977e ("vsock: correct
removal of socket from the list"), which is in all current stable trees
except 4.9.y.

Fixes: d021c344051a ("VSOCK: Introduce VM Sockets")
Signed-off-by: Seth Forshee <sforshee@digitalocean.com>
---
v2: Add Fixes tag and backporting notes.
---
 net/vmw_vsock/af_vsock.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 3235261f138d..38baeb189d4e 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1401,6 +1401,7 @@ static int vsock_connect(struct socket *sock, struct sockaddr *addr,
 			sk->sk_state = sk->sk_state == TCP_ESTABLISHED ? TCP_CLOSING : TCP_CLOSE;
 			sock->state = SS_UNCONNECTED;
 			vsock_transport_cancel_pkt(vsk);
+			vsock_remove_connected(vsk);
 			goto out_wait;
 		} else if (timeout == 0) {
 			err = -ETIMEDOUT;
-- 
2.32.0

On Thu, Feb 17, 2022 at 08:13:12AM -0600, Seth Forshee wrote:
>vsock_connect() expects that the socket could already be in the
>TCP_ESTABLISHED state when the connecting task wakes up with a signal
>pending. If this happens the socket will be in the connected table, and
>it is not removed when the socket state is reset. In this situation it's
>common for the process to retry connect(), and if the connection is
>successful the socket will be added to the connected table a second
>time, corrupting the list.
>
>Prevent this by calling vsock_remove_connected() if a signal is received
>while waiting for a connection. This is harmless if the socket is not in
>the connected table, and if it is in the table then removing it will
>prevent list corruption from a double add.
>
>Note for backporting: this patch requires d5afa82c977e ("vsock: correct
>removal of socket from the list"), which is in all current stable trees
>except 4.9.y.
>
>Fixes: d021c344051a ("VSOCK: Introduce VM Sockets")
>Signed-off-by: Seth Forshee <sforshee@digitalocean.com>
>---
>v2: Add Fixes tag and backporting notes.
>---
> net/vmw_vsock/af_vsock.c | 1 +
> 1 file changed, 1 insertion(+)
>
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index 3235261f138d..38baeb189d4e 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -1401,6 +1401,7 @@ static int vsock_connect(struct socket *sock, struct sockaddr *addr,
> 			sk->sk_state = sk->sk_state == TCP_ESTABLISHED ? TCP_CLOSING : TCP_CLOSE;
> 			sock->state = SS_UNCONNECTED;
> 			vsock_transport_cancel_pkt(vsk);
>+			vsock_remove_connected(vsk);
> 			goto out_wait;
> 		} else if (timeout == 0) {
> 			err = -ETIMEDOUT;
>-- 
>2.32.0
>

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

Hello:

This patch was applied to netdev/net.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Thu, 17 Feb 2022 08:13:12 -0600 you wrote:
> vsock_connect() expects that the socket could already be in the
> TCP_ESTABLISHED state when the connecting task wakes up with a signal
> pending. If this happens the socket will be in the connected table, and
> it is not removed when the socket state is reset. In this situation it's
> common for the process to retry connect(), and if the connection is
> successful the socket will be added to the connected table a second
> time, corrupting the list.
> 
> [...]

Here is the summary with links:
  - [v2] vsock: remove vsock from connected table when connect is interrupted by a signal
    https://git.kernel.org/netdev/net/c/b9208492fcae

You are awesome, thank you!
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