From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760677Ab3B0BAv (ORCPT ); Tue, 26 Feb 2013 20:00:51 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:41997 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760249Ab3BZX5x (ORCPT ); Tue, 26 Feb 2013 18:57:53 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Al Viro Subject: [ 079/150] get rid of unprotected dereferencing of mnt->mnt_ns Date: Tue, 26 Feb 2013 15:55:36 -0800 Message-Id: <20130226235532.334251020@linuxfoundation.org> X-Mailer: git-send-email 1.8.1.rc1.5.g7e0651a In-Reply-To: <20130226235523.930663721@linuxfoundation.org> References: <20130226235523.930663721@linuxfoundation.org> User-Agent: quilt/0.60-2.1.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.8-stable review patch. If anyone has any objections, please let me know. ------------------ From: Al Viro commit 9b40bc90abd126bcc5da5658059b8e72e285e559 upstream. It's safe only under namespace_sem or vfsmount_lock; all places in fs/namespace.c that want mnt->mnt_ns->user_ns actually want to use current->nsproxy->mnt_ns->user_ns (note the calls of check_mnt() in there). Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman --- fs/namespace.c | 29 +++++++++++++++++------------ 1 file changed, 17 insertions(+), 12 deletions(-) --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1237,6 +1237,14 @@ static int do_umount(struct mount *mnt, return retval; } +/* + * Is the caller allowed to modify his namespace? + */ +static inline bool may_mount(void) +{ + return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN); +} + /* * Now umount can handle mount points as well as block devices. * This is important for filesystems which use unnamed block devices. @@ -1255,6 +1263,9 @@ SYSCALL_DEFINE2(umount, char __user *, n if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) return -EINVAL; + if (!may_mount()) + return -EPERM; + if (!(flags & UMOUNT_NOFOLLOW)) lookup_flags |= LOOKUP_FOLLOW; @@ -1268,10 +1279,6 @@ SYSCALL_DEFINE2(umount, char __user *, n if (!check_mnt(mnt)) goto dput_and_out; - retval = -EPERM; - if (!ns_capable(mnt->mnt_ns->user_ns, CAP_SYS_ADMIN)) - goto dput_and_out; - retval = do_umount(mnt, flags); dput_and_out: /* we mustn't call path_put() as that would clear mnt_expiry_mark */ @@ -1295,7 +1302,7 @@ SYSCALL_DEFINE1(oldumount, char __user * static int mount_is_safe(struct path *path) { - if (ns_capable(real_mount(path->mnt)->mnt_ns->user_ns, CAP_SYS_ADMIN)) + if (may_mount()) return 0; return -EPERM; #ifdef notyet @@ -1633,7 +1640,7 @@ static int do_change_type(struct path *p int type; int err = 0; - if (!ns_capable(mnt->mnt_ns->user_ns, CAP_SYS_ADMIN)) + if (!may_mount()) return -EPERM; if (path->dentry != path->mnt->mnt_root) @@ -1797,7 +1804,7 @@ static int do_move_mount(struct path *pa struct mount *p; struct mount *old; int err = 0; - if (!ns_capable(real_mount(path->mnt)->mnt_ns->user_ns, CAP_SYS_ADMIN)) + if (!may_mount()) return -EPERM; if (!old_name || !*old_name) return -EINVAL; @@ -1933,16 +1940,14 @@ static int do_new_mount(struct path *pat int mnt_flags, const char *name, void *data) { struct file_system_type *type; - struct user_namespace *user_ns; + struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns; struct vfsmount *mnt; int err; if (!fstype) return -EINVAL; - /* we need capabilities... */ - user_ns = real_mount(path->mnt)->mnt_ns->user_ns; - if (!ns_capable(user_ns, CAP_SYS_ADMIN)) + if (!may_mount()) return -EPERM; type = get_fs_type(fstype); @@ -2567,7 +2572,7 @@ SYSCALL_DEFINE2(pivot_root, const char _ struct mount *new_mnt, *root_mnt; int error; - if (!ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN)) + if (!may_mount()) return -EPERM; error = user_path_dir(new_root, &new);