From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761650AbbA1EVc (ORCPT ); Tue, 27 Jan 2015 23:21:32 -0500 Received: from mail.kernel.org ([198.145.29.136]:39555 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934178AbbA1EV1 (ORCPT ); Tue, 27 Jan 2015 23:21:27 -0500 From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, "Eric W. Biederman" , Francis Moreau , Zefan Li Subject: [PATCH 3.4 81/91] mnt: Only change user settable mount flags in remount Date: Wed, 28 Jan 2015 12:08:49 +0800 Message-Id: <1422418236-12852-162-git-send-email-lizf@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1422418050-12581-1-git-send-email-lizf@kernel.org> References: <1422418050-12581-1-git-send-email-lizf@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Eric W. Biederman" 3.4.105-rc1 review patch. If anyone has any objections, please let me know. ------------------ commit a6138db815df5ee542d848318e5dae681590fccd upstream. Kenton Varda discovered that by remounting a read-only bind mount read-only in a user namespace the MNT_LOCK_READONLY bit would be cleared, allowing an unprivileged user to the remount a read-only mount read-write. Correct this by replacing the mask of mount flags to preserve with a mask of mount flags that may be changed, and preserve all others. This ensures that any future bugs with this mask and remount will fail in an easy to detect way where new mount flags simply won't change. Acked-by: Serge E. Hallyn Signed-off-by: "Eric W. Biederman" Cc: Francis Moreau Signed-off-by: Zefan Li --- fs/namespace.c | 2 +- include/linux/mount.h | 4 +++- 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index 2985879..f0f2e06 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1681,7 +1681,7 @@ static int do_remount(struct path *path, int flags, int mnt_flags, err = do_remount_sb(sb, flags, data, 0); if (!err) { br_write_lock(vfsmount_lock); - mnt_flags |= mnt->mnt.mnt_flags & MNT_PROPAGATION_MASK; + mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK; mnt->mnt.mnt_flags = mnt_flags; br_write_unlock(vfsmount_lock); } diff --git a/include/linux/mount.h b/include/linux/mount.h index d7029f4..2044aac 100644 --- a/include/linux/mount.h +++ b/include/linux/mount.h @@ -42,7 +42,9 @@ struct mnt_namespace; * flag, consider how it interacts with shared mounts. */ #define MNT_SHARED_MASK (MNT_UNBINDABLE) -#define MNT_PROPAGATION_MASK (MNT_SHARED | MNT_UNBINDABLE) +#define MNT_USER_SETTABLE_MASK (MNT_NOSUID | MNT_NODEV | MNT_NOEXEC \ + | MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME \ + | MNT_READONLY) #define MNT_INTERNAL 0x4000 -- 1.9.1