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copy_tree(): don't link the mounts via mnt_list

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The only place that really needs to be adjusted is commit_tree() -
there we need to iterate through the copy and we might as well
use next_mnt() for that.  However, in case when our tree has been
slid under something already mounted (propagation to a mountpoint
that already has something mounted on it or a 'beneath' move_mount)
we need to take care not to walk into the overmounting tree.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2025-06-17 21:35:22 -04:00
parent dd5a4e1d64
commit 663206854f
3 changed files with 27 additions and 39 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

3
fs/mount.h
View file

@ -193,7 +193,7 @@ static inline bool mnt_ns_empty(const struct mnt_namespace *ns)
return RB_EMPTY_ROOT(&ns->mounts);
}
static inline void move_from_ns(struct mount *mnt, struct list_head *dt_list)
static inline void move_from_ns(struct mount *mnt)
{
struct mnt_namespace *ns = mnt->mnt_ns;
WARN_ON(!mnt_ns_attached(mnt));
@ -203,7 +203,6 @@ static inline void move_from_ns(struct mount *mnt, struct list_head *dt_list)
ns->mnt_first_node = rb_next(&mnt->mnt_node);
rb_erase(&mnt->mnt_node, &ns->mounts);
RB_CLEAR_NODE(&mnt->mnt_node);
list_add_tail(&mnt->mnt_list, dt_list);
}
bool has_locked_children(struct mount *mnt, struct dentry *dentry);

60
fs/namespace.c
View file

@ -1161,34 +1161,6 @@ static void mnt_add_to_ns(struct mnt_namespace *ns, struct mount *mnt)
mnt_notify_add(mnt);
}
/*
* vfsmount lock must be held for write
*/
static void commit_tree(struct mount *mnt)
{
struct mount *parent = mnt->mnt_parent;
struct mount *m;
LIST_HEAD(head);
struct mnt_namespace *n = parent->mnt_ns;
BUG_ON(parent == mnt);
if (!mnt_ns_attached(mnt)) {
list_add_tail(&head, &mnt->mnt_list);
while (!list_empty(&head)) {
m = list_first_entry(&head, typeof(*m), mnt_list);
list_del(&m->mnt_list);
mnt_add_to_ns(n, m);
}
n->nr_mounts += n->pending_mounts;
n->pending_mounts = 0;
}
make_visible(mnt);
touch_mnt_namespace(n);
}
static struct mount *next_mnt(struct mount *p, struct mount *root)
{
struct list_head *next = p->mnt_mounts.next;
@ -1215,6 +1187,27 @@ static struct mount *skip_mnt_tree(struct mount *p)
return p;
}
/*
* vfsmount lock must be held for write
*/
static void commit_tree(struct mount *mnt)
{
struct mnt_namespace *n = mnt->mnt_parent->mnt_ns;
if (!mnt_ns_attached(mnt)) {
for (struct mount *m = mnt; m; m = next_mnt(m, mnt))
if (unlikely(mnt_ns_attached(m)))
m = skip_mnt_tree(m);
else
mnt_add_to_ns(n, m);
n->nr_mounts += n->pending_mounts;
n->pending_mounts = 0;
}
make_visible(mnt);
touch_mnt_namespace(n);
}
/**
* vfs_create_mount - Create a mount for a configured superblock
* @fc: The configuration context with the superblock attached
@ -1831,9 +1824,8 @@ static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
for (p = mnt; p; p = next_mnt(p, mnt)) {
p->mnt.mnt_flags |= MNT_UMOUNT;
if (mnt_ns_attached(p))
move_from_ns(p, &tmp_list);
else
list_move(&p->mnt_list, &tmp_list);
move_from_ns(p);
list_add_tail(&p->mnt_list, &tmp_list);
}
/* Hide the mounts from mnt_mounts */
@ -2270,7 +2262,6 @@ struct mount *copy_tree(struct mount *src_root, struct dentry *dentry,
list_add(&dst_mnt->mnt_expire,
&src_mnt->mnt_expire);
}
list_add_tail(&dst_mnt->mnt_list, &res->mnt_list);
attach_mnt(dst_mnt, dst_parent, src_parent->mnt_mp);
unlock_mount_hash();
}
@ -2686,12 +2677,9 @@ static int attach_recursive_mnt(struct mount *source_mnt,
list_del_init(&source_mnt->mnt_expire);
} else {
if (source_mnt->mnt_ns) {
LIST_HEAD(head);
/* move from anon - the caller will destroy */
for (p = source_mnt; p; p = next_mnt(p, source_mnt))
move_from_ns(p, &head);
list_del_init(&head);
move_from_ns(p);
}
}

3
fs/pnode.c
View file

@ -449,7 +449,8 @@ static void umount_one(struct mount *m, struct list_head *to_umount)
{
m->mnt.mnt_flags |= MNT_UMOUNT;
list_del_init(&m->mnt_child);
move_from_ns(m, to_umount);
move_from_ns(m);
list_add_tail(&m->mnt_list, to_umount);
}
static void remove_from_candidate_list(struct mount *m)