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    SubjectRe: [PATCH] fs: Remove implicit nodev for new mounts in non-root userns
    Quoting Andy Lutomirski (luto@amacapital.net):
    > On Fri, Aug 15, 2014 at 12:05 PM, Serge Hallyn <serge.hallyn@ubuntu.com> wrote:
    > > Quoting Andy Lutomirski (luto@amacapital.net):
    > >> Currently, creating a new mount (as opposed to bindmount) in a
    > >> non-root userns will implicitly set nodev unless the fs is devpts.
    > >> Something like this will be necessary for file systems that allow
    > >> the mounter to create device nodes without using mknod (e.g. FUSE
    > >> if/when that is allowed), but none of the currently allowed
    > >> filesystems do this.
    > >
    > > Hi,
    > >
    > > Sorry, I'm probably thinking stupidly, but I don't see this restriction
    > > being the case
    > >
    > > serge@sl:~$ mount | grep tmp
    > > [...]
    > > tmpfs on /run type tmpfs (rw,noexec,nosuid,size=10%,mode=0755)
    > > serge@sl:~$ sudo mknod /run/kvm c 10 232
    > > [sudo] password for serge:
    > > serge@sl:~$ echo $?
    > > 0
    > > serge@sl:~$ ls -l /run/kvm
    > > crw-r--r-- 1 root root 10, 232 Aug 15 14:04 /run/kvm
    > >
    > > But you seem to be saying I shouldn't be allowed to create a device inside
    > > a tmpfs. What am I overlooking?
    >
    > I assume you're in the root userns. This patch is unnecessary, and
    > has no effect, if you're in the root userns.

    Right, but I thought you were justifying adding FS_USERNS_DEV_MOUNT by saying
    that you cannot mknod in those filesystems. But I see you actually said
    "without using mknod". I guess I don't understand that caveat.

    -serge


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