Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751712AbaJOXJS (ORCPT ); Wed, 15 Oct 2014 19:09:18 -0400 Received: from mail-lb0-f172.google.com ([209.85.217.172]:41878 "EHLO mail-lb0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751227AbaJOXJQ (ORCPT ); Wed, 15 Oct 2014 19:09:16 -0400 MIME-Version: 1.0 In-Reply-To: <20141015152013.GB988@ubuntu-mba51> References: <1413296756-25071-1-git-send-email-seth.forshee@canonical.com> <1413296756-25071-6-git-send-email-seth.forshee@canonical.com> <543E8BAD.7000207@mit.edu> <20141015152013.GB988@ubuntu-mba51> From: Andy Lutomirski Date: Wed, 15 Oct 2014 16:08:54 -0700 Message-ID: Subject: Re: [PATCH v4 5/5] fuse: Allow user namespace mounts To: Andy Lutomirski , Miklos Szeredi , fuse-devel@lists.sourceforge.net, "linux-kernel@vger.kernel.org" , Linux FS Devel , "Eric W. Biederman" , "Serge H. Hallyn" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 15, 2014 at 8:20 AM, Seth Forshee wrote: > On Wed, Oct 15, 2014 at 07:58:53AM -0700, Andy Lutomirski wrote: >> On 10/14/2014 07:25 AM, Seth Forshee wrote: >> > Cc: Eric W. Biederman >> > Cc: Serge H. Hallyn >> > Signed-off-by: Seth Forshee >> > --- >> > fs/fuse/inode.c | 4 ++-- >> > 1 file changed, 2 insertions(+), 2 deletions(-) >> > >> > diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c >> > index 5e00a6a76049..6522926b14e4 100644 >> > --- a/fs/fuse/inode.c >> > +++ b/fs/fuse/inode.c >> > @@ -1212,7 +1212,7 @@ static void fuse_kill_sb_anon(struct super_block *sb) >> > static struct file_system_type fuse_fs_type = { >> > .owner = THIS_MODULE, >> > .name = "fuse", >> > - .fs_flags = FS_HAS_SUBTYPE, >> > + .fs_flags = FS_HAS_SUBTYPE | FS_USERNS_MOUNT, >> > .mount = fuse_mount, >> > .kill_sb = fuse_kill_sb_anon, >> > }; >> > @@ -1244,7 +1244,7 @@ static struct file_system_type fuseblk_fs_type = { >> > .name = "fuseblk", >> > .mount = fuse_mount_blk, >> > .kill_sb = fuse_kill_sb_blk, >> > - .fs_flags = FS_REQUIRES_DEV | FS_HAS_SUBTYPE, >> > + .fs_flags = FS_REQUIRES_DEV | FS_HAS_SUBTYPE | FS_USERNS_MOUNT, >> >> I think it's decision time -- if these patches are applied, then FUSE >> will be the first filesystem for which userns nodev behavior matters for >> security, so applying this patch will enshrine an API decision. >> >> I would very much prefer to make this patch depend on this: >> >> http://lkml.kernel.org/g/2686c32f00b14148379e8cfee9c028c794d4aa1a.1407974494.git.luto@amacapital.net >> >> That change will require that anyone who tries to mount one of these >> things explicitly requests MS_NODEV instead of keeping the current >> behavior of implicitly setting MS_NODEV and possibly confusing user code >> that tries to remount. >> >> If you like my patch, feel free to fold it in to your series, or Eric >> can apply it directly (pretty please). >> >> For background, with your patches as is, if you mount a FUSE fs and then >> remount it with identical flags, the remount is likely to fail. > > I discussed this with Eric during LinuxCon NA ... as I recall he was > undecided about whether or not to use your patch at the time. I do > prefer an explicit failure over implicitly adding MS_NODEV, but it's not > up to me. I do agree though that we should make a decision before > merging the fuse patches, I was just assuming that the decision was > already made. As far as I know, no decision has been made. I discussed it with Eric at LinuxCon NA, too. Too bad we didn't meet there. Hopefully your patches will convince him to ack my patch :) --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/