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From: Peter Zijlstra <peterz@infradead.org>
To: Oleg Nesterov <oleg@redhat.com>
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 16:59:49 +0100	[thread overview]
Message-ID: <20170314155949.GE32474@worktop> (raw)
In-Reply-To: <20170314152625.GP5680@worktop>

On Tue, Mar 14, 2017 at 04:26:25PM +0100, Peter Zijlstra wrote:
> A well.. I'll go do the 'trivial' patch then.

A little like so; completely untested.

---
 kernel/events/core.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 110b38a58493..6576449b6029 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -10346,6 +10346,17 @@ void perf_event_free_task(struct task_struct *task)
 			continue;
 
 		mutex_lock(&ctx->mutex);
+		raw_spin_lock_irq(&ctx->lock);
+		/*
+		 * Destroy the task <-> ctx relation and mark the context dead.
+		 *
+		 * This is important because even though the task hasn't been
+		 * exposed yet the context has been (through child_list).
+		 */
+		RCU_INIT_POINTER(task->perf_event_ctxp[ctxn], NULL);
+		WRITE_ONCE(ctx->task, TASK_TOMBSTONE);
+		put_task_struct(task); /* cannot be last */
+		raw_spin_unlock_irq(&ctx->lock);
 again:
 		list_for_each_entry_safe(event, tmp, &ctx->pinned_groups,
 				group_entry)

  reply	other threads:[~2017-03-14 17:37 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
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 [this message]
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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