current->nsproxy is should not be accessed directly as syzbot has found
that it could be NULL at times, causing crashes.  Fix up the af_vsock
sysctl handlers to use container_of() to deal with the current net
namespace instead of attempting to rely on current.

This is the same type of change done in commit 7f5611cbc487 ("rds:
sysctl: rds_tcp_{rcv,snd}buf: avoid using current->nsproxy")

Cc: Stefano Garzarella <sgarzare@redhat.com>
Cc: stable <stable@kernel.org>
Assisted-by: gkh_clanker_2000
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

Note, this is compile-tested only.  Some of my scripts found this when
looking for places that are missing fixes that were applied to other
parts of the kernel.  I think the af_vsock code uses namespaces, but as
I don't know the network stack at all I figured I would let you all
review it to tell me how wrong I got this change and all is fine with
the original code.

thanks,

greg k-h

 net/vmw_vsock/af_vsock.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index 9880756d9eff..f4062c6a1944 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c

@@ -2825,7 +2825,7 @@ static int vsock_net_mode_string(const struct ctl_table *table, int write,
 	if (write)
 		return -EPERM;
 
-	net = current->nsproxy->net_ns;
+	net = container_of(table->data, struct net, vsock.mode);
 
 	return __vsock_net_mode_string(table, write, buffer, lenp, ppos,
 				       vsock_net_mode(net), NULL);

@@ -2838,7 +2838,7 @@ static int vsock_net_child_mode_string(const struct ctl_table *table, int write,
 	struct net *net;
 	int ret;
 
-	net = current->nsproxy->net_ns;
+	net = container_of(table->data, struct net, vsock.child_ns_mode);
 
 	ret = __vsock_net_mode_string(table, write, buffer, lenp, ppos,
 				      vsock_net_child_mode(net), &new_mode);

-- 
2.53.0