From mboxrd@z Thu Jan 1 00:00:00 1970 From: Djalal Harouni Subject: Re: [PATCH v4 10/21] fs: Check for invalid i_uid in may_follow_link() Date: Tue, 24 May 2016 16:55:26 +0100 Message-ID: <20160524155526.GB2830@dztty.fritz.box> References: <1461699396-33000-1-git-send-email-seth.forshee@canonical.com> <1461699396-33000-11-git-send-email-seth.forshee@canonical.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1461699396-33000-11-git-send-email-seth.forshee@canonical.com> Sender: linux-kernel-owner@vger.kernel.org To: Seth Forshee Cc: "Eric W. Biederman" , Alexander Viro , Serge Hallyn , Richard Weinberger , Austin S Hemmelgarn , Miklos Szeredi , Pavel Tikhomirov , linux-kernel@vger.kernel.org, linux-bcache@vger.kernel.org, dm-devel@redhat.com, linux-raid@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, cgroups@vger.kernel.org List-Id: linux-raid.ids On Tue, Apr 26, 2016 at 02:36:23PM -0500, 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 Reviewed-by: Djalal Harouni > --- > 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 a29094c6f4a1..6fe8b0d8ca90 100644 > --- a/fs/namei.c > +++ b/fs/namei.c > @@ -915,7 +915,7 @@ 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); > -- > 2.7.4 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Djalal Harouni http://opendz.org