tree 686a142254d360a963f010bb573f4db5fb83e7bc
parent 80f232121b69cc69a31ccb2b38c1665d770b0710
author Al Viro <viro@zeniv.linux.org.uk> 1557383548 -0400
committer Al Viro <viro@zeniv.linux.org.uk> 1557383570 -0400

do_move_mount(): fix an unsafe use of is_anon_ns()

What triggers it is a race between mount --move and umount -l
of the source; we should reject it (the source is parentless *and*
not the root of anon namespace at that), but the check for namespace
being an anon one is broken in that case - is_anon_ns() needs
ns to be non-NULL.  Better fixed here than in is_anon_ns(), since
the rest of the callers is guaranteed to get a non-NULL argument...

Reported-by: syzbot+494c7ddf66acac0ad747@syzkaller.appspotmail.com
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>