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authorAl Viro <viro@zeniv.linux.org.uk>2020-04-27 10:26:22 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2020-04-27 10:37:14 -0400
commitb0d3869ce9eeacbb1bbd541909beeef4126426d5 (patch)
treed710d97e4dfff49cea1b0267bf0bfb149e7bcd04 /fs/pnode.c
parent3815f1be546e752327b5868af103ccdddcc4db77 (diff)
propagate_one(): mnt_set_mountpoint() needs mount_lock
... 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>
Diffstat (limited to 'fs/pnode.c')
-rw-r--r--fs/pnode.c9
1 files changed, 4 insertions, 5 deletions
diff --git a/fs/pnode.c b/fs/pnode.c
index 49f6d7ff2139..1106137c747a 100644
--- 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);
}