From: Al Viro <v...@zeniv.linux.org.uk>
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 <piot...@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: sta...@kernel.org
Signed-off-by: Al Viro <v...@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
fs/pnode.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -261,14 +261,13 @@ static int propagate_one(struct mount *m
child = copy_tree(last_source, last_source->mnt.mnt_root, type);
if (IS_ERR(child))
return PTR_ERR(child);
+ 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);
}
