linux-kernel - Re: [PATCH] signal: Fix the error return of kill -1

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Date:   Wed, 16 Aug 2023 15:32:26 -0500
From:   "Eric W. Biederman" <ebiederm@...ssion.com>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     David Laight <David.Laight@...LAB.COM>,
        Petr Skocik <pskocik@...il.com>,
        Kees Cook <keescook@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Marco Elver <elver@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] signal: Fix the error return of kill -1

Oleg Nesterov <oleg@...hat.com> writes:

> On 08/15, David Laight wrote:
>>
>> or maybe even:
>> 	} else {
>> 		struct task_struct * p;
>> 		int err;
>> 		ret = -ESRCH;
>>
>> 		for_each_process(p) {
>> 			if (task_pid_vnr(p) > 1 &&
>> 					!same_thread_group(p, current)) {
>> 				err = group_send_sig_info(sig, info, p,
>> 							  PIDTYPE_MAX);
>> 				if (ret)
>> 					ret = err;
>
> Hmm, indeed ;)
>
> and "err" can be declared inside the loop.

We can't remove the success case, from my posted patch.

A signal is considered as successfully delivered if at least
one process receives it.

That is something the current code for kill -1 actually gets
wrong (but hides because it ignores -EPERM).

Otherwise yes I expect we can simplify the use of variables as
suggested.

Eric