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-rw-r--r--fs/namespace.c130
1 files changed, 79 insertions, 51 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
index 487ba30bb5c6..cc1375eff88c 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -15,6 +15,7 @@
#include <linux/user_namespace.h>
#include <linux/namei.h>
#include <linux/security.h>
+#include <linux/cred.h>
#include <linux/idr.h>
#include <linux/init.h> /* init_rootfs */
#include <linux/fs_struct.h> /* get_fs_root et.al. */
@@ -24,6 +25,8 @@
#include <linux/magic.h>
#include <linux/bootmem.h>
#include <linux/task_work.h>
+#include <linux/sched/task.h>
+
#include "pnode.h"
#include "internal.h"
@@ -637,28 +640,6 @@ struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
}
/*
- * find the last mount at @dentry on vfsmount @mnt.
- * mount_lock must be held.
- */
-struct mount *__lookup_mnt_last(struct vfsmount *mnt, struct dentry *dentry)
-{
- struct mount *p, *res = NULL;
- p = __lookup_mnt(mnt, dentry);
- if (!p)
- goto out;
- if (!(p->mnt.mnt_flags & MNT_UMOUNT))
- res = p;
- hlist_for_each_entry_continue(p, mnt_hash) {
- if (&p->mnt_parent->mnt != mnt || p->mnt_mountpoint != dentry)
- break;
- if (!(p->mnt.mnt_flags & MNT_UMOUNT))
- res = p;
- }
-out:
- return res;
-}
-
-/*
* lookup_mnt - Return the first child mount mounted at path
*
* "First" means first mounted chronologically. If you create the
@@ -878,6 +859,13 @@ void mnt_set_mountpoint(struct mount *mnt,
hlist_add_head(&child_mnt->mnt_mp_list, &mp->m_list);
}
+static void __attach_mnt(struct mount *mnt, struct mount *parent)
+{
+ 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
*/
@@ -886,28 +874,45 @@ static void attach_mnt(struct mount *mnt,
struct mountpoint *mp)
{
mnt_set_mountpoint(parent, mp, mnt);
- hlist_add_head_rcu(&mnt->mnt_hash, m_hash(&parent->mnt, mp->m_dentry));
- list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
+ __attach_mnt(mnt, parent);
}
-static void attach_shadowed(struct mount *mnt,
- struct mount *parent,
- struct mount *shadows)
+void mnt_change_mountpoint(struct mount *parent, struct mountpoint *mp, struct mount *mnt)
{
- if (shadows) {
- hlist_add_behind_rcu(&mnt->mnt_hash, &shadows->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);
- }
+ struct mountpoint *old_mp = mnt->mnt_mp;
+ struct dentry *old_mountpoint = mnt->mnt_mountpoint;
+ struct mount *old_parent = mnt->mnt_parent;
+
+ list_del_init(&mnt->mnt_child);
+ hlist_del_init(&mnt->mnt_mp_list);
+ hlist_del_init_rcu(&mnt->mnt_hash);
+
+ attach_mnt(mnt, parent, mp);
+
+ put_mountpoint(old_mp);
+
+ /*
+ * Safely avoid even the suggestion this code might sleep or
+ * lock the mount hash by taking advantage of the knowledge that
+ * mnt_change_mountpoint will not release the final reference
+ * to a mountpoint.
+ *
+ * During mounting, the mount passed in as the parent mount will
+ * continue to use the old mountpoint and during unmounting, the
+ * old mountpoint will continue to exist until namespace_unlock,
+ * which happens well after mnt_change_mountpoint.
+ */
+ spin_lock(&old_mountpoint->d_lock);
+ old_mountpoint->d_lockref.count--;
+ spin_unlock(&old_mountpoint->d_lock);
+
+ mnt_add_count(old_parent, -1);
}
/*
* vfsmount lock must be held for write
*/
-static void commit_tree(struct mount *mnt, struct mount *shadows)
+static void commit_tree(struct mount *mnt)
{
struct mount *parent = mnt->mnt_parent;
struct mount *m;
@@ -925,7 +930,7 @@ static void commit_tree(struct mount *mnt, struct mount *shadows)
n->mounts += n->pending_mounts;
n->pending_mounts = 0;
- attach_shadowed(mnt, parent, shadows);
+ __attach_mnt(mnt, parent);
touch_mnt_namespace(n);
}
@@ -989,6 +994,21 @@ vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void
}
EXPORT_SYMBOL_GPL(vfs_kern_mount);
+struct vfsmount *
+vfs_submount(const struct dentry *mountpoint, struct file_system_type *type,
+ const char *name, void *data)
+{
+ /* Until it is worked out how to pass the user namespace
+ * through from the parent mount to the submount don't support
+ * unprivileged mounts with submounts.
+ */
+ if (mountpoint->d_sb->s_user_ns != &init_user_ns)
+ return ERR_PTR(-EPERM);
+
+ return vfs_kern_mount(type, MS_SUBMOUNT, name, data);
+}
+EXPORT_SYMBOL_GPL(vfs_submount);
+
static struct mount *clone_mnt(struct mount *old, struct dentry *root,
int flag)
{
@@ -1764,7 +1784,6 @@ 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);
@@ -1786,14 +1805,7 @@ struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
goto out;
lock_mount_hash();
list_add_tail(&q->mnt_list, &res->mnt_list);
- 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);
+ attach_mnt(q, parent, p->mnt_mp);
unlock_mount_hash();
}
}
@@ -1992,10 +2004,18 @@ static int attach_recursive_mnt(struct mount *source_mnt,
{
HLIST_HEAD(tree_list);
struct mnt_namespace *ns = dest_mnt->mnt_ns;
+ struct mountpoint *smp;
struct mount *child, *p;
struct hlist_node *n;
int err;
+ /* Preallocate a mountpoint in case the new mounts need
+ * to be tucked under other mounts.
+ */
+ smp = get_mountpoint(source_mnt->mnt.mnt_root);
+ if (IS_ERR(smp))
+ return PTR_ERR(smp);
+
/* Is there space to add these mounts to the mount namespace? */
if (!parent_path) {
err = count_mounts(ns, source_mnt);
@@ -2022,16 +2042,19 @@ static int attach_recursive_mnt(struct mount *source_mnt,
touch_mnt_namespace(source_mnt->mnt_ns);
} else {
mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);
- commit_tree(source_mnt, NULL);
+ commit_tree(source_mnt);
}
hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) {
struct mount *q;
hlist_del_init(&child->mnt_hash);
- q = __lookup_mnt_last(&child->mnt_parent->mnt,
- child->mnt_mountpoint);
- commit_tree(child, q);
+ q = __lookup_mnt(&child->mnt_parent->mnt,
+ child->mnt_mountpoint);
+ if (q)
+ mnt_change_mountpoint(child, smp, q);
+ commit_tree(child);
}
+ put_mountpoint(smp);
unlock_mount_hash();
return 0;
@@ -2046,6 +2069,11 @@ static int attach_recursive_mnt(struct mount *source_mnt,
cleanup_group_ids(source_mnt, NULL);
out:
ns->pending_mounts = 0;
+
+ read_seqlock_excl(&mount_lock);
+ put_mountpoint(smp);
+ read_sequnlock_excl(&mount_lock);
+
return err;
}
@@ -2794,7 +2822,7 @@ long do_mount(const char *dev_name, const char __user *dir_name,
flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN |
MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
- MS_STRICTATIME | MS_NOREMOTELOCK);
+ MS_STRICTATIME | MS_NOREMOTELOCK | MS_SUBMOUNT);
if (flags & MS_REMOUNT)
retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,