tree 6a0bb053fd2dfa7690b63cef6764dc15e232198b
parent 105a0cd0821b99ed15065fec57bfd9c6eb305128
author Al Viro <viro@zeniv.linux.org.uk> 1348229942 -0400
committer chrmhoffmann <chrmhoffmann@gmail.com> 1532289026 +0200

do_add_mount()/umount -l races

normally we deal with lock_mount()/umount races by checking that
mountpoint to be is still in our namespace after lock_mount() has
been done.  However, do_add_mount() skips that check when called
with MNT_SHRINKABLE in flags (i.e. from finish_automount()).  The
reason is that ->mnt_ns may be a temporary namespace created exactly
to contain automounts a-la NFS4 referral handling.  It's not the
namespace of the caller, though, so check_mnt() would fail here.
We still need to check that ->mnt_ns is non-NULL in that case,
though.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
(cherry picked from commit 156cacb1d0d36b0d0582d9e798e58e0044f516b3)
Signed-off-by: Kevin F. Haggerty <haggertk@lineageos.org>

Change-Id: I9d46068a03fb338d587212a8377ac983cd831159