[PATCH] vsock: remove vsock from connected table when connect is interrupted by a signal

[PATCH] vsock: remove vsock from connected table when connect is interrupted by a signal

[Seth Forshee]

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.

Signed-off-by: Seth Forshee <sforshee@digitalocean.com>
---
 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

Re: [PATCH] vsock: remove vsock from connected table when connect is interrupted by a signal

[Stefano Garzarella]

Hi Seth,

On Wed, Feb 16, 2022 at 08:32:22AM -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.
>
>Signed-off-by: Seth Forshee <sforshee@digitalocean.com>
>---
> 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
>

Thanks for this fix! The patch LGTM:

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


@Dave, @Jakub, since we need this also in stable branches, I was going 
to suggest adding a Fixes tag, but I'm a little confused: the issue 
seems to have always been there, so from commit d021c344051a ("VSOCK: 
Introduce VM Sockets"), but to use vsock_remove_connected() as we are 
using in this patch, we really need commit d5afa82c977e ("vsock: correct 
removal of socket from the list").

Commit d5afa82c977e was introduces in v5.3 and it was backported in 
v4.19 and v4.14, but not in v4.9.
So if we want to backport this patch also for v4.9, I think we need 
commit d5afa82c977e as well.

Thanks,
Stefano

Re: [PATCH] vsock: remove vsock from connected table when connect is interrupted by a signal

[Jakub Kicinski]

On Wed, 16 Feb 2022 17:11:22 +0100 Stefano Garzarella wrote:
> On Wed, Feb 16, 2022 at 08:32:22AM -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.
> >
> >Signed-off-by: Seth Forshee <sforshee@digitalocean.com>
> >---
> > 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;
> 
> Thanks for this fix! The patch LGTM:
> 
> Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
> 
> 
> @Dave, @Jakub, since we need this also in stable branches, I was going 
> to suggest adding a Fixes tag, but I'm a little confused: the issue 
> seems to have always been there, so from commit d021c344051a ("VSOCK: 
> Introduce VM Sockets"), but to use vsock_remove_connected() as we are 
> using in this patch, we really need commit d5afa82c977e ("vsock: correct 
> removal of socket from the list").
> 
> Commit d5afa82c977e was introduces in v5.3 and it was backported in 
> v4.19 and v4.14, but not in v4.9.
> So if we want to backport this patch also for v4.9, I think we need 
> commit d5afa82c977e as well.

The fixes tag sounds good. Dunno what's the best way to handle this
case. We can add a mention of the dependency to the patch description.
Personally I'd keep things simple, add the Fixes tag and keep an eye
on the backports, if 4.9 doesn't get it - email Greg and explain.

Re: [PATCH] vsock: remove vsock from connected table when connect is interrupted by a signal

[Stefano Garzarella]

On Wed, Feb 16, 2022 at 08:14:59PM -0800, Jakub Kicinski wrote:
>On Wed, 16 Feb 2022 17:11:22 +0100 Stefano Garzarella wrote:
>> On Wed, Feb 16, 2022 at 08:32:22AM -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.
>> >
>> >Signed-off-by: Seth Forshee <sforshee@digitalocean.com>
>> >---
>> > 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;
>>
>> Thanks for this fix! The patch LGTM:
>>
>> Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
>>
>>
>> @Dave, @Jakub, since we need this also in stable branches, I was going
>> to suggest adding a Fixes tag, but I'm a little confused: the issue
>> seems to have always been there, so from commit d021c344051a ("VSOCK:
>> Introduce VM Sockets"), but to use vsock_remove_connected() as we are
>> using in this patch, we really need commit d5afa82c977e ("vsock: correct
>> removal of socket from the list").
>>
>> Commit d5afa82c977e was introduces in v5.3 and it was backported in
>> v4.19 and v4.14, but not in v4.9.
>> So if we want to backport this patch also for v4.9, I think we need
>> commit d5afa82c977e as well.
>
>The fixes tag sounds good. Dunno what's the best way to handle this
>case. We can add a mention of the dependency to the patch description.
>Personally I'd keep things simple, add the Fixes tag and keep an eye
>on the backports, if 4.9 doesn't get it - email Greg and explain.
>

Okay, I'll keep an eye on this patch for 4.9.

@Seth, can you send a v2 mentioning the dependency with commit 
d5afa82c977e ("vsock: correct removal of socket from the list") and 
adding the following fixes tag?

     Fixes: d021c344051a ("VSOCK: Introduce VM Sockets")

Thanks,
Stefano