linux-kernel - Re: + make-good_sigevent-non-static.patch added to -mm tree

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Message-ID: <20070125154324.GA183@tv-sign.ru>
Date:	Thu, 25 Jan 2007 18:43:24 +0300
From:	Oleg Nesterov <oleg@...sign.ru>
To:	sebastien.dugue@...l.net
Cc:	Zach Brown <zach.brown@...cle.com>,
	Suparna Bhattacharya <suparna@...ibm.com>,
	Benjamin LaHaise <bcrl@...ck.org>,
	Ulrich Drepper <drepper@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...l.org>, linux-kernel@...r.kernel.org
Subject: Re: + make-good_sigevent-non-static.patch added to -mm tree

SИbastien DuguИ wrote:
>
> +struct task_struct *good_sigevent(sigevent_t *event)
> +{
> +	struct task_struct *task = current->group_leader;
> +
> +	if ((event->sigev_notify & SIGEV_THREAD_ID) == SIGEV_THREAD_ID) {
> +		task = find_task_by_pid(event->sigev_notify_thread_id);
> +
> +		if (!task || task->tgid != current->tgid)
> +			return NULL;
> +	} else if (event->sigev_notify == SIGEV_SIGNAL) {

No, no, we can't use "else" here,

> +		if (event->sigev_signo <= 0 || event->sigev_signo > SIGRTMAX)

because we skip the check above in SIGEV_THREAD_ID case.

This way any user can crash the kernel with a minimal effort.

Oleg.

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