tree 1328bd9e2b49c3553662e564e27cd01a8fb3e236
parent 38faccf5f918330394a33ed8266f98b43525869b
author Al Viro <viro@zeniv.linux.org.uk> 1587997582 -0400
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1588433161 +0200

propagate_one(): mnt_set_mountpoint() needs mount_lock

commit b0d3869ce9eeacbb1bbd541909beeef4126426d5 upstream.

... to protect the modification of mp->m_count done by it.  Most of
the places that modify that thing also have namespace_lock held,
but not all of them can do so, so we really need mount_lock here.
Kudos to Piotr Krysiuk <piotras@gmail.com>, who'd spotted a related
bug in pivot_root(2) (fixed unnoticed in 5.3); search for other
similar turds has caught out this one.

Cc: stable@kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Piotr Krysiuk <piotras@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>