From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Seth Forshee , Serge Hallyn , "Eric W. Biederman" Subject: [PATCH 4.7 05/59] fs: Check for invalid i_uid in may_follow_link() Date: Mon, 12 Sep 2016 17:29:25 +0200 Message-Id: <20160912152128.980769300@linuxfoundation.org> In-Reply-To: <20160912152128.765864031@linuxfoundation.org> References: <20160912152128.765864031@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.7-stable review patch. If anyone has any objections, please let me know. ------------------ From: Seth Forshee commit 2d7f9e2ad35e4e7a3086231f19bfab33c6a8a64a upstream. Filesystem uids which don't map into a user namespace may result in inode->i_uid being INVALID_UID. A symlink and its parent could have different owners in the filesystem can both get mapped to INVALID_UID, which may result in following a symlink when this would not have otherwise been permitted when protected symlinks are enabled. Signed-off-by: Seth Forshee Acked-by: Serge Hallyn Signed-off-by: Eric W. Biederman Signed-off-by: Greg Kroah-Hartman --- fs/namei.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/fs/namei.c +++ b/fs/namei.c @@ -901,6 +901,7 @@ static inline int may_follow_link(struct { const struct inode *inode; const struct inode *parent; + kuid_t puid; if (!sysctl_protected_symlinks) return 0; @@ -916,7 +917,8 @@ static inline int may_follow_link(struct return 0; /* Allowed if parent directory and link owner match. */ - if (uid_eq(parent->i_uid, inode->i_uid)) + puid = parent->i_uid; + if (uid_valid(puid) && uid_eq(puid, inode->i_uid)) return 0; if (nd->flags & LOOKUP_RCU)