On Wed, Apr 3, 2013 at 11:43 AM, Eric Dumazet <eric.duma...@gmail.com> wrote:
> On Wed, 2013-04-03 at 10:58 -0700, Andy Lutomirski wrote:
>
>>
>> This sounds suspiciously like an SCM_CREDENTIALS bug triggered by a
>> race. There's a fix (that needs both a new version from me and a review
>> by someone) here:
>>
>> http://www.spinics.net/lists/netdev/msg229948.html
>
> Hmm... this is not a stable candidate, IMHO.
Agreed.
>
> This has to be fixed (if needed) in a more easy way.
>
> What about this one liner ?
>
> CC Eric W. Biederman as he wrote commit
> dbe9a4173ea53b72b2c3
> (scm: Don't use struct ucred in NETLINK_CB and struct scm_cookie.)
>
> diff --git a/include/net/scm.h b/include/net/scm.h
> index 975cca0..42359d8 100644
> --- a/include/net/scm.h
> +++ b/include/net/scm.h
> @@ -120,7 +120,7 @@ static __inline__ void scm_recv(struct socket *sock,
> struct msghdr *msg,
> return;
> }
>
> - if (test_bit(SOCK_PASSCRED, &sock->flags)) {
> + if (test_bit(SOCK_PASSCRED, &sock->flags) && scm->creds.pid) {
> struct user_namespace *current_ns = current_user_ns();
> struct ucred ucreds = {
> .pid = scm->creds.pid,
>
>
That looks like it's correct. If it gets applied, I'll respin my
patches on top of it.
(This approach may be a POSIX violation for all I know, and it's even
possible that some really fragile userspace breaks. But I doubt it,
and anything that will break as a result is already operating in a
highly confused state; hence the original problem.)
--Andy
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