Commit 94b4120f authored Dec 07, 2019 by Aleksa Sarai Committed by Greg Kroah-Hartman Mar 05, 2020

namei: only return -ECHILD from follow_dotdot_rcu()



commit 2b98149c2377bff12be5dd3ce02ae0506e2dd613 upstream.

It's over-zealous to return hard errors under RCU-walk here, given that
a REF-walk will be triggered for all other cases handling ".." under
RCU.

The original purpose of this check was to ensure that if a rename occurs
such that a directory is moved outside of the bind-mount which the
resolution started in, it would be detected and blocked to avoid being
able to mess with paths outside of the bind-mount. However, triggering a
new REF-walk is just as effective a solution.

Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Fixes: 397d425d ("vfs: Test for and handle paths that are unreachable from their mnt_root")
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent c5521f96

fs/namei.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1368,7 +1368,7 @@ static int follow_dotdot_rcu(struct nameidata *nd)
		nd->path.dentry = parent;
		nd->seq = seq;
		if (unlikely(!path_connected(&nd->path)))
		return -ENOENT;
		return -ECHILD;
		break;
		} else {
		struct mount *mnt = real_mount(nd->path.mnt);