tree 1525239f0724b2b9ff84c84153927ef5a8f45021
parent 72f0d0bf51362011c4d841a89fb8f5cfb16e0bf3
author Greg Kurz <groug@kaod.org> 1488148980 +0100
committer Greg Kurz <groug@kaod.org> 1488277275 +0100

9pfs: local: unlinkat: don't follow symlinks

The local_unlinkat() callback is vulnerable to symlink attacks because it
calls remove() which follows symbolic links in all path elements but the
rightmost one.

This patch converts local_unlinkat() to rely on opendir_nofollow() and
unlinkat() instead.

Most of the code is moved to a separate local_unlinkat_common() helper
which will be reused in a subsequent patch to fix the same issue in
local_remove().

This partly fixes CVE-2016-9602.

Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>