Re: [PATCH RESEND v2 16/18] fuse: Support fuse filesystems outside of init_user_ns

On Wed, Mar 9, 2016 at 3:18 PM, Seth Forshee [off-list ref] wrote:

On Wed, Mar 09, 2016 at 12:29:23PM +0100, Miklos Szeredi wrote:

quoted

On Mon, Jan 04, 2016 at 12:03:55PM -0600, Seth Forshee wrote:

quoted

quoted

-static int parse_fuse_opt(char *opt, struct fuse_mount_data *d, int is_bdev)
+static int parse_fuse_opt(char *opt, struct fuse_mount_data *d, int is_bdev,
+                     struct user_namespace *user_ns)
 {
    char *p;
    memset(d, 0, sizeof(struct fuse_mount_data));
    d->max_read = ~0;
    d->blksize = FUSE_DEFAULT_BLKSIZE;
+   d->user_id = make_kuid(user_ns, 0);
+   d->group_id = make_kgid(user_ns, 0);

It is true that if "user_id=" or "group_id" options were omitted we used the
zero uid/gid values.  However, this isn't actually used by anybody AFAIK, and
generalizing it for userns doesn't seem to make much sense.

So I suggest we that we instead return an error if mounting from a userns AND
neither "allow_other" nor both "user_id" and "group_id" are specified.

But those are also used for ownership of the connection files in
fusectl. In an allow_other mount shouldn't those files by owned by
namespace root and not global root?

Yes.

Can't we use current_cred()->uid/gid? Or fsuid/fsgid maybe?

When we have true unprivileged mounts, the user_id/group_id options
become redundant anyway and we can just use the current credentials.

Thanks,
Miklos

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