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authorAl Viro <viro@zeniv.linux.org.uk>2014-03-20 21:10:51 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2014-03-30 19:18:51 -0400
commit38129a13e6e71f666e0468e99fdd932a687b4d7e (patch)
tree438e817fdf7d224f9fda1186eb24b1bbc37a4b5c /fs/pnode.c
parent0b1b901b5a98bb36943d10820efc796f7cd45ff3 (diff)
downloadlinux-linaro-stable-38129a13e6e71f666e0468e99fdd932a687b4d7e.tar.gz
switch mnt_hash to hlist
fixes RCU bug - walking through hlist is safe in face of element moves, since it's self-terminating. Cyclic lists are not - if we end up jumping to another hash chain, we'll loop infinitely without ever hitting the original list head. [fix for dumb braino folded] Spotted by: Max Kellermann <mk@cm4all.com> Cc: stable@vger.kernel.org Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/pnode.c')
-rw-r--r--fs/pnode.c26
1 files changed, 15 insertions, 11 deletions
diff --git a/fs/pnode.c b/fs/pnode.c
index c7221bb19801..88396df725b4 100644
--- a/fs/pnode.c
+++ b/fs/pnode.c
@@ -220,14 +220,14 @@ static struct mount *get_source(struct mount *dest,
* @tree_list : list of heads of trees to be attached.
*/
int propagate_mnt(struct mount *dest_mnt, struct mountpoint *dest_mp,
- struct mount *source_mnt, struct list_head *tree_list)
+ struct mount *source_mnt, struct hlist_head *tree_list)
{
struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
struct mount *m, *child;
int ret = 0;
struct mount *prev_dest_mnt = dest_mnt;
struct mount *prev_src_mnt = source_mnt;
- LIST_HEAD(tmp_list);
+ HLIST_HEAD(tmp_list);
for (m = propagation_next(dest_mnt, dest_mnt); m;
m = propagation_next(m, dest_mnt)) {
@@ -246,27 +246,29 @@ int propagate_mnt(struct mount *dest_mnt, struct mountpoint *dest_mp,
child = copy_tree(source, source->mnt.mnt_root, type);
if (IS_ERR(child)) {
ret = PTR_ERR(child);
- list_splice(tree_list, tmp_list.prev);
+ tmp_list = *tree_list;
+ tmp_list.first->pprev = &tmp_list.first;
+ INIT_HLIST_HEAD(tree_list);
goto out;
}
if (is_subdir(dest_mp->m_dentry, m->mnt.mnt_root)) {
mnt_set_mountpoint(m, dest_mp, child);
- list_add_tail(&child->mnt_hash, tree_list);
+ hlist_add_head(&child->mnt_hash, tree_list);
} else {
/*
* This can happen if the parent mount was bind mounted
* on some subdirectory of a shared/slave mount.
*/
- list_add_tail(&child->mnt_hash, &tmp_list);
+ hlist_add_head(&child->mnt_hash, &tmp_list);
}
prev_dest_mnt = m;
prev_src_mnt = child;
}
out:
lock_mount_hash();
- while (!list_empty(&tmp_list)) {
- child = list_first_entry(&tmp_list, struct mount, mnt_hash);
+ while (!hlist_empty(&tmp_list)) {
+ child = hlist_entry(tmp_list.first, struct mount, mnt_hash);
umount_tree(child, 0);
}
unlock_mount_hash();
@@ -338,8 +340,10 @@ static void __propagate_umount(struct mount *mnt)
* umount the child only if the child has no
* other children
*/
- if (child && list_empty(&child->mnt_mounts))
- list_move_tail(&child->mnt_hash, &mnt->mnt_hash);
+ if (child && list_empty(&child->mnt_mounts)) {
+ hlist_del_init_rcu(&child->mnt_hash);
+ hlist_add_before_rcu(&child->mnt_hash, &mnt->mnt_hash);
+ }
}
}
@@ -350,11 +354,11 @@ static void __propagate_umount(struct mount *mnt)
*
* vfsmount lock must be held for write
*/
-int propagate_umount(struct list_head *list)
+int propagate_umount(struct hlist_head *list)
{
struct mount *mnt;
- list_for_each_entry(mnt, list, mnt_hash)
+ hlist_for_each_entry(mnt, list, mnt_hash)
__propagate_umount(mnt);
return 0;
}