[Devel] Re: [RFC 4/5] user namespaces: allow killing tasks in your own or child userns

[Eric W. Biederman]

"Serge E. Hallyn" <serge at hallyn.com> writes:

> Changelog:
> 	Dec 8: Fixed bug in my check_kill_permission pointed out by
> 	       Eric Biederman.
> 	Dec 13: Apply Eric's suggestion to pass target task into kill_ok_by_cred()
> 	        for clarity
>
> Signed-off-by: Serge E. Hallyn <serge.hallyn at canonical.com>
> ---
>  kernel/signal.c |   33 ++++++++++++++++++++++++++++-----
>  1 files changed, 28 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/signal.c b/kernel/signal.c
> index 4e3cff1..499bd36 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -659,11 +686,7 @@ static int check_kill_permission(int sig, struct siginfo *info,
>  	cred = current_cred();
>  	tcred = __task_cred(t);
Nit pick  you don't need to compute cred and tcred here now.

>  	if (!same_thread_group(current, t) &&
> -	    (cred->euid ^ tcred->suid) &&
> -	    (cred->euid ^ tcred->uid) &&
> -	    (cred->uid  ^ tcred->suid) &&
> -	    (cred->uid  ^ tcred->uid) &&
> -	    !capable(CAP_KILL)) {
> +	    !kill_ok_by_cred(t)) {
>  		switch (sig) {
>  		case SIGCONT:
>  			sid = task_session(t);
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