vsock: Use container_of() to get net namespace in sysctl handlers

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 7f5611c ("rds:
sysctl: rds_tcp_{rcv,snd}buf: avoid using current->nsproxy")

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Bobby Eshleman <bobbyeshleman@meta.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Fixes: eafb64f ("vsock: add netns to vsock core")
Link: https://patch.msgid.link/2026022318-rearview-gallery-ae13@gregkh
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: gregkh

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);