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 <ebiederm@xxxxxxxxxxxx>
> > Cc: Serge H. Hallyn <serge.hallyn@xxxxxxxxxx>
> > Signed-off-by: Seth Forshee <seth.forshee@xxxxxxxxxxxxx>
> > ---
> > 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@xxxxxxxxxxxxxx
>
> 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.
(Resending my response since I still don't see it on lkml after 7+
hours)
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.
Thanks,
Seth
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