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Serge E. Hallyn wrote:
> The problem is that when you run a setuid binary, its pP and pE are
> fully raised. The following patch fixes it for me. Chris, does it fix
> your problem? Andrew, am I again confusing myself and doing something
> unsafe?
I think this is yet another example of the fragile mess that is UID
emulation with capabilities. Your patch is an example of privilege
escalation - luser can kill a more-capable process. In the kill CONT
case we reached the opposite conclusion to this one. As was the case
then, I didn't disagree then :*). If it meets folk's expectations, then
this is probably a good patch...
> --- a/security/commoncap.c
> +++ b/security/commoncap.c
> @@ -543,6 +543,9 @@ int cap_task_kill(struct task_struct *p, struct siginfo *info,
> if (capable(CAP_KILL))
> return 0;
>
> + if (p->euid==0 && p->uid==current->uid)
> + return 0;
> +
Its late and I'm obviously tired, but is there any reason not to simply use:
if (p->uid == current->uid)
return 0;
Whatever the case, could you put the new code closer to the sig ==
SIGCONT test? The capability tests are at the end of cap_task_kill() and
this new check breaks that pattern.
Cheers
Andrew
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