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authorAl Viro <viro@zeniv.linux.org.uk>2014-08-10 03:44:55 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2014-08-11 12:28:10 -0400
commit12a5b5294cb1896e9a3c9fca8ff5a7e3def4e8c6 (patch)
tree9a3780d90c484e1a18e37b980d3d6cf2ac766711 /fs
parent60bb45297f7551833346c5cebc6d483ea17ea5f2 (diff)
downloadlinux-stericsson-12a5b5294cb1896e9a3c9fca8ff5a7e3def4e8c6.tar.gz
fix copy_tree() regression
Since 3.14 we had copy_tree() get the shadowing wrong - if we had one vfsmount shadowing another (i.e. if A is a slave of B, C is mounted on A/foo, then D got mounted on B/foo creating D' on A/foo shadowed by C), copy_tree() of A would make a copy of D' shadow the the copy of C, not the other way around. It's easy to fix, fortunately - just make sure that mount follows the one that shadows it in mnt_child as well as in mnt_hash, and when copy_tree() decides to attach a new mount, check if the last child it has added to the same parent should be shadowing the new one. And if it should, just use the same logics commit_tree() has - put the new mount into the hash and children lists right after the one that should shadow it. Cc: stable@vger.kernel.org [3.14 and later] Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs')
-rw-r--r--fs/namespace.c31
1 files changed, 24 insertions, 7 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index 65af9d0e0d67..be3f6f23a47d 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -778,6 +778,20 @@ static void attach_mnt(struct mount *mnt,
list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
}
+static void attach_shadowed(struct mount *mnt,
+ struct mount *parent,
+ struct mount *shadows)
+{
+ if (shadows) {
+ hlist_add_after_rcu(&shadows->mnt_hash, &mnt->mnt_hash);
+ list_add(&mnt->mnt_child, &shadows->mnt_child);
+ } else {
+ hlist_add_head_rcu(&mnt->mnt_hash,
+ m_hash(&parent->mnt, mnt->mnt_mountpoint));
+ list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
+ }
+}
+
/*
* vfsmount lock must be held for write
*/
@@ -796,12 +810,7 @@ static void commit_tree(struct mount *mnt, struct mount *shadows)
list_splice(&head, n->list.prev);
- if (shadows)
- hlist_add_after_rcu(&shadows->mnt_hash, &mnt->mnt_hash);
- else
- hlist_add_head_rcu(&mnt->mnt_hash,
- m_hash(&parent->mnt, mnt->mnt_mountpoint));
- list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
+ attach_shadowed(mnt, parent, shadows);
touch_mnt_namespace(n);
}
@@ -1474,6 +1483,7 @@ struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
continue;
for (s = r; s; s = next_mnt(s, r)) {
+ struct mount *t = NULL;
if (!(flag & CL_COPY_UNBINDABLE) &&
IS_MNT_UNBINDABLE(s)) {
s = skip_mnt_tree(s);
@@ -1495,7 +1505,14 @@ struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
goto out;
lock_mount_hash();
list_add_tail(&q->mnt_list, &res->mnt_list);
- attach_mnt(q, parent, p->mnt_mp);
+ mnt_set_mountpoint(parent, p->mnt_mp, q);
+ if (!list_empty(&parent->mnt_mounts)) {
+ t = list_last_entry(&parent->mnt_mounts,
+ struct mount, mnt_child);
+ if (t->mnt_mp != p->mnt_mp)
+ t = NULL;
+ }
+ attach_shadowed(q, parent, t);
unlock_mount_hash();
}
}