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FAILED: patch "[PATCH] ovl: prevent private clone if bind mount is not allowed" failed to apply to 4.4-stable tree

PATCH [email protected] 1 participant 1 message Aug 13, 2021

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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 <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 427215d85e8d1476da1a86b8d67aceb485eb3631 Mon Sep 17 00:00:00 2001
From: Miklos Szeredi <[email protected]>
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 <[email protected]>
Fixes c771d683a62e ("vfs: introduce clone_private_mount()")
Cc <[email protected]> # v3.18
Signed-off-by Miklos Szeredi <[email protected]>
fs/namespace.c +28 -14
index ab4174a3c802..f79d9471cb76 100644
@@ -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);