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From: Oleg Nesterov <oleg@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Dmitry Vyukov <dvyukov@google.com>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	syzkaller <syzkaller@googlegroups.com>
Subject: Re: perf: use-after-free in perf_release
Date: Tue, 14 Mar 2017 14:24:27 +0100	[thread overview]
Message-ID: <20170314132427.GA27369@redhat.com> (raw)
In-Reply-To: <20170314125508.GK3343@twins.programming.kicks-ass.net>

On 03/14, Peter Zijlstra wrote:
>
> On Tue, Mar 07, 2017 at 05:51:32PM +0100, Oleg Nesterov wrote:
>
> > inherit_event() returns NULL under is_orphaned_event() check, not ERR_PTR().
> > Is it correct?
>
> Yes. This is all a tad tricky, but it seems to be correct.
>
> By returning NULL, not an error, we affect the silent discard of
> orphaned events. This is correct, because otherwise
> perf_event_release_kernel() would have come by and explicitly discarded
> those events for us anyway.

Thanks... I'll try to understand this later.

> @@ -10608,7 +10627,6 @@ inherit_task_group(struct perf_event *event, struct task_struct *parent,
>  		 * First allocate and initialize a context for the
>  		 * child.
>  		 */
> -
>  		child_ctx = alloc_perf_context(parent_ctx->pmu, child);
>  		if (!child_ctx)
>  			return -ENOMEM;
> @@ -10670,7 +10688,7 @@ static int perf_event_init_context(struct task_struct *child, int ctxn)
>  		ret = inherit_task_group(event, parent, parent_ctx,
>  					 child, ctxn, &inherited_all);
>  		if (ret)
> -			break;
> +			goto out_unlock;
>  	}
>  
>  	/*
> @@ -10686,7 +10704,7 @@ static int perf_event_init_context(struct task_struct *child, int ctxn)
>  		ret = inherit_task_group(event, parent, parent_ctx,
>  					 child, ctxn, &inherited_all);
>  		if (ret)
> -			break;
> +			goto out_unlock;

With this change you can also simplify inherit_task_group() a little bit,
it no longer needs to nullify *inherited_all if inherit_group() fails.

Oleg.

  reply	other threads:[~2017-03-14 13:26 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-06  9:57 Dmitry Vyukov
2017-03-06 12:13 ` Peter Zijlstra
2017-03-06 12:17   ` Dmitry Vyukov
2017-03-06 12:23     ` Peter Zijlstra
2017-03-06 12:27       ` Dmitry Vyukov
2017-03-06 12:47         ` Peter Zijlstra
2017-03-06 13:14 ` Peter Zijlstra
2017-03-06 13:34   ` Dmitry Vyukov
2017-03-07  9:08     ` Peter Zijlstra
2017-03-07  9:26       ` Dmitry Vyukov
2017-03-07  9:37         ` Peter Zijlstra
2017-03-07  9:43           ` Dmitry Vyukov
2017-03-07 10:00             ` Peter Zijlstra
2017-03-07 13:16   ` Peter Zijlstra
2017-03-07 13:27     ` Peter Zijlstra
2017-03-07 14:04   ` Oleg Nesterov
2017-03-07 14:17     ` Dmitry Vyukov
2017-03-07 16:51       ` Oleg Nesterov
2017-03-07 17:29         ` Peter Zijlstra
2017-03-14 12:55         ` Peter Zijlstra
2017-03-14 13:24           ` Oleg Nesterov [this message]
2017-03-14 13:47             ` Peter Zijlstra
2017-03-14 14:03           ` Oleg Nesterov
2017-03-14 14:07             ` Peter Zijlstra
2017-03-14 14:30               ` Oleg Nesterov
2017-03-14 15:02                 ` Peter Zijlstra
2017-03-14 15:07                   ` Peter Zijlstra
2017-03-14 15:37                     ` Oleg Nesterov
2017-03-14 15:46                       ` Peter Zijlstra
2017-03-14 15:19                   ` Oleg Nesterov
2017-03-14 15:26                     ` Peter Zijlstra
2017-03-14 15:59                       ` Peter Zijlstra
2017-03-15 16:43                         ` Oleg Nesterov
2017-03-16 12:05                           ` Peter Zijlstra
2017-03-16 13:57                           ` Peter Zijlstra
2017-03-16 16:41                             ` Oleg Nesterov
2017-03-16 12:47 [PATCH 0/4] perf patches Peter Zijlstra
2017-03-16 12:47 ` [PATCH 1/4] perf: Fix use-after-free in perf_release() Peter Zijlstra
2017-03-16 15:19   ` [tip:perf/urgent] perf/core: " tip-bot for Peter Zijlstra
2017-03-16 12:47 ` [PATCH 2/4] perf: Fix event inheritance on fork() Peter Zijlstra
2017-03-16 15:19   ` [tip:perf/urgent] perf/core: " tip-bot for Peter Zijlstra
2017-03-16 12:47 ` [PATCH 3/4] perf: Simplify perf_event_free_task() Peter Zijlstra
2017-03-16 15:20   ` [tip:perf/urgent] perf/core: " tip-bot for Peter Zijlstra
2017-03-16 12:47 ` [PATCH 4/4] perf: Better explain the inherit magic Peter Zijlstra
2017-03-16 15:21   ` [tip:perf/urgent] perf/core: " tip-bot for Peter Zijlstra
2017-03-16 13:20 ` [PATCH 0/4] perf patches Ingo Molnar

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