commit 88da52ccd66e65f2e63a6c35c9dff55d448ef4dc upstream.
The WARN_ON_ONCE() in collect_domain_accesses() can be triggered when
trying to link a root mount point. This cannot work in practice because
this directory is mounted, but the VFS check is done after the call to
security_path_link().
Do not use source directory's d_parent when the source directory is the
mount point.
Cc: Günther Noack <gnoack@google.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: stable@vger.kernel.org
Reported-by: syzbot+bf4903dc7e12b18ebc87@syzkaller.appspotmail.com
Fixes: b91c3e4ea7 ("landlock: Add support for file reparenting with LANDLOCK_ACCESS_FS_REFER")
Closes: https://lore.kernel.org/r/000000000000553d3f0618198200@google.com
Link: https://lore.kernel.org/r/20240516181935.1645983-2-mic@digikod.net
[mic: Fix commit message]
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
cc30d05b34