From: Seth Forshee <seth.forshee-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org> To: "Eric W. Biederman" <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>, Alexander Viro <viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org> Cc: Serge Hallyn <serge.hallyn-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>, Seth Forshee <seth.forshee-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>, dm-devel-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, Miklos Szeredi <miklos-sUDqSbJrdHQHWmgEVkV9KA@public.gmane.org>, linux-security-module-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-bcache-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-raid-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, fuse-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, Austin S Hemmelgarn <ahferroin7-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, linux-mtd-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, selinux-+05T5uksL2qpZYMLLGbcSA@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Subject: [PATCH v2 07/18] fs: Check for invalid i_uid in may_follow_link() Date: Mon, 7 Dec 2015 15:21:16 -0600 [thread overview] Message-ID: <1449523289-144238-8-git-send-email-seth.forshee@canonical.com> (raw) In-Reply-To: <1449523289-144238-1-git-send-email-seth.forshee-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org> 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 <seth.forshee-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org> Acked-by: Serge Hallyn <serge.hallyn-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org> --- 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 ------------------------------------------------------------------------------ Go from Idea to Many App Stores Faster with Intel(R) XDK Give your users amazing mobile app experiences with Intel(R) XDK. Use one codebase in this all-in-one HTML5 development environment. Design, debug & build mobile apps & 2D/3D high-impact games for multiple OSs. http://pubads.g.doubleclick.net/gampad/clk?id=254741911&iu=/4140
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From: Seth Forshee <seth.forshee@canonical.com> To: "Eric W. Biederman" <ebiederm@xmission.com>, Alexander Viro <viro@zeniv.linux.org.uk> Cc: Serge Hallyn <serge.hallyn@canonical.com>, Richard Weinberger <richard.weinberger@gmail.com>, Austin S Hemmelgarn <ahferroin7@gmail.com>, Miklos Szeredi <miklos@szeredi.hu>, 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 <seth.forshee@canonical.com> Subject: [PATCH v2 07/18] fs: Check for invalid i_uid in may_follow_link() Date: Mon, 7 Dec 2015 15:21:16 -0600 [thread overview] Message-ID: <1449523289-144238-8-git-send-email-seth.forshee@canonical.com> (raw) In-Reply-To: <1449523289-144238-1-git-send-email-seth.forshee@canonical.com> 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 <seth.forshee@canonical.com> Acked-by: Serge Hallyn <serge.hallyn@canonical.com> --- 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
next prev parent reply other threads:[~2015-12-07 21:21 UTC|newest] Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-12-07 21:21 [PATCH v2 00/19] Support fuse mounts in user namespaces Seth Forshee 2015-12-07 21:21 ` [PATCH v2 03/18] fs: Treat foreign mounts as nosuid Seth Forshee 2015-12-07 21:21 ` [PATCH v2 04/18] selinux: Add support for unprivileged mounts from user namespaces Seth Forshee [not found] ` <1449523289-144238-1-git-send-email-seth.forshee-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org> 2015-12-07 21:21 ` [PATCH v2 01/18] block_dev: Support checking inode permissions in lookup_bdev() Seth Forshee 2015-12-07 21:21 ` Seth Forshee 2015-12-07 21:21 ` [PATCH v2 02/18] block_dev: Check permissions towards block device inode when mounting Seth Forshee 2015-12-07 21:21 ` Seth Forshee 2015-12-07 21:21 ` [PATCH v2 05/18] userns: Replace in_userns with current_in_userns Seth Forshee 2015-12-07 21:21 ` Seth Forshee 2015-12-07 21:21 ` [PATCH v2 06/18] Smack: Handle labels consistently in untrusted mounts Seth Forshee 2015-12-07 21:21 ` Seth Forshee 2015-12-07 21:21 ` Seth Forshee [this message] 2015-12-07 21:21 ` [PATCH v2 07/18] fs: Check for invalid i_uid in may_follow_link() Seth Forshee 2015-12-07 21:21 ` [PATCH v2 08/18] cred: Reject inodes with invalid ids in set_create_file_as() Seth Forshee 2015-12-07 21:21 ` Seth Forshee 2015-12-07 21:21 ` [PATCH v2 09/18] fs: Refuse uid/gid changes which don't map into s_user_ns Seth Forshee 2015-12-07 21:21 ` Seth Forshee 2015-12-07 21:21 ` [PATCH v2 10/18] fs: Update posix_acl support to handle user namespace mounts Seth Forshee 2015-12-07 21:21 ` Seth Forshee 2015-12-07 21:21 ` [PATCH v2 11/18] fs: Ensure the mounter of a filesystem is privileged towards its inodes Seth Forshee 2015-12-07 21:21 ` Seth Forshee 2015-12-07 21:21 ` [PATCH v2 12/18] fs: Don't remove suid for CAP_FSETID in s_user_ns Seth Forshee 2015-12-07 21:21 ` Seth Forshee 2015-12-07 21:21 ` [PATCH v2 15/18] fuse: Add support for pid namespaces Seth Forshee 2015-12-07 21:21 ` Seth Forshee 2015-12-07 21:21 ` [PATCH v2 16/18] fuse: Support fuse filesystems outside of init_user_ns Seth Forshee 2015-12-07 21:21 ` Seth Forshee 2015-12-07 21:21 ` [PATCH v2 17/18] fuse: Restrict allow_other to the superblock's namespace or a descendant Seth Forshee 2015-12-07 21:21 ` Seth Forshee 2015-12-07 21:21 ` [PATCH v2 18/18] fuse: Allow user namespace mounts Seth Forshee 2015-12-07 21:21 ` Seth Forshee 2015-12-07 21:21 ` [PATCH v2 13/18] fs: Allow superblock owner to access do_remount_sb() Seth Forshee 2015-12-07 21:21 ` [PATCH v2 14/18] capabilities: Allow privileged user in s_user_ns to set security.* xattrs Seth Forshee
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