When binding a non-abstract AF_UNIX socket it will gain a representation
in the filesystem. Enable the socket infrastructure to handle idmapped
mounts by passing down the user namespace of the mount the socket will
be created from. If the initial user namespace is passed nothing changes
so non-idmapped mounts will see identical behavior as before.

Cc: Christoph Hellwig <hch@lst.de>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <redacted>
---
/* v2 */
unchanged

/* v3 */
unchanged

/* v4 */
unchanged

/* v5 */
base-commit: 7c53f6b671f4aba70ff15e1b05148b10d58c2837
---
 net/unix/af_unix.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index b4987805e5e5..4be33240e9cc 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c

@@ -996,7 +996,7 @@ static int unix_mknod(const char *sun_path, umode_t mode, struct path *res)
 	 */
 	err = security_path_mknod(&path, dentry, mode, 0);
 	if (!err) {
-		err = vfs_mknod(&init_user_ns, d_inode(path.dentry), dentry, mode, 0);
+		err = vfs_mknod(mnt_user_ns(path.mnt), d_inode(path.dentry), dentry, mode, 0);
 		if (!err) {
 			res->mnt = mntget(path.mnt);
 			res->dentry = dget(dentry);

-- 
2.30.0