From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Eric W. Biederman" Subject: [REVIEW][PATCH 4/6] fs: Allow superblock owner to access do_remount_sb() Date: Wed, 23 May 2018 18:25:36 -0500 Message-ID: <20180523232538.4880-4-ebiederm__34148.6523313963$1527117908$gmane$org@xmission.com> References: <87o9h6554f.fsf@xmission.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <87o9h6554f.fsf-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Linux Containers Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Seth Forshee , "Eric W. Biederman" , linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Christian Brauner List-Id: containers.vger.kernel.org Superblock level remounts are currently restricted to global CAP_SYS_ADMIN, as is the path for changing the root mount to read only on umount. Loosen both of these permission checks to also allow CAP_SYS_ADMIN in any namespace which is privileged towards the userns which originally mounted the filesystem. Signed-off-by: Seth Forshee Acked-by: "Eric W. Biederman" Acked-by: Serge Hallyn Signed-off-by: Eric W. Biederman --- fs/namespace.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index 5f75969adff1..8ddd14806799 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1590,7 +1590,7 @@ static int do_umount(struct mount *mnt, int flags) * Special case for "unmounting" root ... * we just try to remount it readonly. */ - if (!capable(CAP_SYS_ADMIN)) + if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) return -EPERM; down_write(&sb->s_umount); if (!sb_rdonly(sb)) @@ -2333,7 +2333,7 @@ static int do_remount(struct path *path, int ms_flags, int sb_flags, down_write(&sb->s_umount); if (ms_flags & MS_BIND) err = change_mount_flags(path->mnt, ms_flags); - else if (!capable(CAP_SYS_ADMIN)) + else if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) err = -EPERM; else err = do_remount_sb(sb, sb_flags, data, 0); -- 2.14.1