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author | Al Viro <viro@zeniv.linux.org.uk> | 2014-08-10 03:44:55 -0400 |
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committer | Al Viro <viro@zeniv.linux.org.uk> | 2014-08-11 12:28:10 -0400 |
commit | 12a5b5294cb1896e9a3c9fca8ff5a7e3def4e8c6 (patch) | |
tree | 9a3780d90c484e1a18e37b980d3d6cf2ac766711 /fs/namespace.c | |
parent | 60bb45297f7551833346c5cebc6d483ea17ea5f2 (diff) | |
download | lwn-12a5b5294cb1896e9a3c9fca8ff5a7e3def4e8c6.tar.gz lwn-12a5b5294cb1896e9a3c9fca8ff5a7e3def4e8c6.zip |
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/namespace.c')
-rw-r--r-- | fs/namespace.c | 31 |
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(); } } |