FAILED: patch "[PATCH] ovl: prevent private clone if bind mount is not allowed" failed to apply to 4.4-stable tree
From: <gregkh@linuxfoundation.org>
Date: 2021-08-13 09:02:09
Subsystem:
filesystems (vfs and infrastructure), the rest · Maintainers:
Alexander Viro, Christian Brauner, Linus Torvalds
The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to [off-list ref].
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 427215d85e8d1476da1a86b8d67aceb485eb3631 Mon Sep 17 00:00:00 2001
From: Miklos Szeredi <redacted>
Date: Mon, 9 Aug 2021 10:19:47 +0200
Subject: [PATCH] ovl: prevent private clone if bind mount is not allowed
Add the following checks from __do_loopback() to clone_private_mount() as
well:
- verify that the mount is in the current namespace
- verify that there are no locked children
Reported-by: Alois Wohlschlager <redacted>
Fixes: c771d683a62e ("vfs: introduce clone_private_mount()")
Cc: <redacted> # v3.18
Signed-off-by: Miklos Szeredi <redacted>
diff --git a/fs/namespace.c b/fs/namespace.c
index ab4174a3c802..f79d9471cb76 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c@@ -1938,6 +1938,20 @@ void drop_collected_mounts(struct vfsmount *mnt) namespace_unlock(); } +static bool has_locked_children(struct mount *mnt, struct dentry *dentry) +{ + struct mount *child; + + list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { + if (!is_subdir(child->mnt_mountpoint, dentry)) + continue; + + if (child->mnt.mnt_flags & MNT_LOCKED) + return true; + } + return false; +} + /** * clone_private_mount - create a private clone of a path * @path: path to clone
@@ -1953,10 +1967,19 @@ struct vfsmount *clone_private_mount(const struct path *path) struct mount *old_mnt = real_mount(path->mnt); struct mount *new_mnt; + down_read(&namespace_sem); if (IS_MNT_UNBINDABLE(old_mnt)) - return ERR_PTR(-EINVAL); + goto invalid; + + if (!check_mnt(old_mnt)) + goto invalid; + + if (has_locked_children(old_mnt, path->dentry)) + goto invalid; new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE); + up_read(&namespace_sem); + if (IS_ERR(new_mnt)) return ERR_CAST(new_mnt);
@@ -1964,6 +1987,10 @@ struct vfsmount *clone_private_mount(const struct path *path) new_mnt->mnt_ns = MNT_NS_INTERNAL; return &new_mnt->mnt; + +invalid: + up_read(&namespace_sem); + return ERR_PTR(-EINVAL); } EXPORT_SYMBOL_GPL(clone_private_mount);
@@ -2315,19 +2342,6 @@ static int do_change_type(struct path *path, int ms_flags) return err; } -static bool has_locked_children(struct mount *mnt, struct dentry *dentry) -{ - struct mount *child; - list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { - if (!is_subdir(child->mnt_mountpoint, dentry)) - continue; - - if (child->mnt.mnt_flags & MNT_LOCKED) - return true; - } - return false; -} - static struct mount *__do_loopback(struct path *old_path, int recurse) { struct mount *mnt = ERR_PTR(-EINVAL), *old = real_mount(old_path->mnt);