Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754847AbbLDQm7 (ORCPT ); Fri, 4 Dec 2015 11:42:59 -0500 Received: from h2.hallyn.com ([78.46.35.8]:41453 "EHLO h2.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753979AbbLDQm5 (ORCPT ); Fri, 4 Dec 2015 11:42:57 -0500 Date: Fri, 4 Dec 2015 10:42:55 -0600 From: "Serge E. Hallyn" To: Seth Forshee Cc: "Eric W. Biederman" , Alexander Viro , 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 Subject: Re: [PATCH 07/19] fs: Check for invalid i_uid in may_follow_link() Message-ID: <20151204164255.GC1722@mail.hallyn.com> References: <1449070821-73820-1-git-send-email-seth.forshee@canonical.com> <1449070821-73820-8-git-send-email-seth.forshee@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1449070821-73820-8-git-send-email-seth.forshee@canonical.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2440 Lines: 69 On Wed, Dec 02, 2015 at 09:40:07AM -0600, Seth Forshee wrote: > 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/ -- 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/