This is a note to let you know that I've just added the patch titled
propagate_one(): mnt_set_mountpoint() needs mount_lock
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
propagate_one-mnt_set_mountpoint-needs-mount_lock.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b0d3869ce9eeacbb1bbd541909beeef4126426d5 Mon Sep 17 00:00:00 2001
From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Date: Mon, 27 Apr 2020 10:26:22 -0400
Subject: propagate_one(): mnt_set_mountpoint() needs mount_lock
From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
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@xxxxxxxxx>, 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@xxxxxxxxxx
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Piotr Krysiuk <piotras@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/pnode.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -268,14 +268,13 @@ static int propagate_one(struct mount *m
if (IS_ERR(child))
return PTR_ERR(child);
child->mnt.mnt_flags &= ~MNT_LOCKED;
+ read_seqlock_excl(&mount_lock);
mnt_set_mountpoint(m, mp, child);
+ if (m->mnt_master != dest_master)
+ SET_MNT_MARK(m->mnt_master);
+ read_sequnlock_excl(&mount_lock);
last_dest = m;
last_source = child;
- if (m->mnt_master != dest_master) {
- read_seqlock_excl(&mount_lock);
- SET_MNT_MARK(m->mnt_master);
- read_sequnlock_excl(&mount_lock);
- }
hlist_add_head(&child->mnt_hash, list);
return count_mounts(m->mnt_ns, child);
}
Patches currently in stable-queue which might be from viro@xxxxxxxxxxxxxxxxxx are
queue-4.4/kernel-gcov-fs.c-gcov_seq_next-should-increase-posit.patch
queue-4.4/ipc-util.c-sysvipc_find_ipc-should-increase-position.patch
queue-4.4/fs-namespace.c-fix-mountpoint-reference-counter-race.patch
queue-4.4/propagate_one-mnt_set_mountpoint-needs-mount_lock.patch
