Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933089AbbLGVXf (ORCPT ); Mon, 7 Dec 2015 16:23:35 -0500 Received: from mail-io0-f172.google.com ([209.85.223.172]:34796 "EHLO mail-io0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932722AbbLGVX1 (ORCPT ); Mon, 7 Dec 2015 16:23:27 -0500 From: Seth Forshee To: "Eric W. Biederman" , Alexander Viro Cc: Serge Hallyn , Richard Weinberger , Austin S Hemmelgarn , Miklos Szeredi , linux-bcache@vger.kernel.org, dm-devel@redhat.com, linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org, linux-fsdevel@vger.kernel.org, fuse-devel@lists.sourceforge.net, linux-security-module@vger.kernel.org, selinux@tycho.nsa.gov, Seth Forshee Subject: [PATCH v2 07/18] fs: Check for invalid i_uid in may_follow_link() Date: Mon, 7 Dec 2015 15:21:16 -0600 Message-Id: <1449523289-144238-8-git-send-email-seth.forshee@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1449523289-144238-1-git-send-email-seth.forshee@canonical.com> References: <1449523289-144238-1-git-send-email-seth.forshee@canonical.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2011 Lines: 61 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. Add a new helper function, uid_valid_eq(), and use this to validate that the ids in may_follow_link() are both equal and valid. Also add an equivalent helper for gids, which is currently unused. Signed-off-by: Seth Forshee Acked-by: Serge Hallyn --- fs/namei.c | 2 +- include/linux/uidgid.h | 10 ++++++++++ 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/fs/namei.c b/fs/namei.c index 288e8a74bf88..4ccafd391697 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -902,7 +902,7 @@ static inline int may_follow_link(struct nameidata *nd) return 0; /* Allowed if parent directory and link owner match. */ - if (uid_eq(parent->i_uid, inode->i_uid)) + if (uid_valid_eq(parent->i_uid, inode->i_uid)) return 0; if (nd->flags & LOOKUP_RCU) diff --git a/include/linux/uidgid.h b/include/linux/uidgid.h index 03835522dfcb..e09529fe2668 100644 --- a/include/linux/uidgid.h +++ b/include/linux/uidgid.h @@ -117,6 +117,16 @@ static inline bool gid_valid(kgid_t gid) return __kgid_val(gid) != (gid_t) -1; } +static inline bool uid_valid_eq(kuid_t left, kuid_t right) +{ + return uid_eq(left, right) && uid_valid(left); +} + +static inline bool gid_valid_eq(kgid_t left, kgid_t right) +{ + return gid_eq(left, right) && gid_valid(left); +} + #ifdef CONFIG_USER_NS extern kuid_t make_kuid(struct user_namespace *from, uid_t uid); -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/