Commit 05cbaa28 authored Dec 30, 2009 by Peter Zijlstra Committed by Ingo Molnar Dec 31, 2009

perf: Fix NULL deref in inheritance code



Liming found a NULL deref when a task has a perf context but no
counters  when it forks.

This can occur in two cases, a race during construction where
the fork hits after installing the context but before the first
counter gets inserted, or more reproducably, a fork after the
last counter is closed (which leaves the context around).

Reported-by: Wang Liming <liming.wang@windriver.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
CC: <stable@kernel.org>
LKML-Reference: <1262185684.7135.222.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent 48b5ba9c

kernel/perf_event.c

+2 −3

Original line number	Diff line number	Diff line
		@@ -5148,7 +5148,7 @@ int perf_event_init_task(struct task_struct *child)
		GFP_KERNEL);
		if (!child_ctx) {
		ret = -ENOMEM;
		goto exit;
		break;
		}

		__perf_event_init_context(child_ctx, child);
		@@ -5164,7 +5164,7 @@ int perf_event_init_task(struct task_struct *child)
		}
		}

		if (inherited_all) {
		if (child_ctx && inherited_all) {
		/*
		* Mark the child context as a clone of the parent
		* context, or of whatever the parent is a clone of.
		@@ -5184,7 +5184,6 @@ int perf_event_init_task(struct task_struct *child)
		get_ctx(child_ctx->parent_ctx);
		}

		exit:
		mutex_unlock(&parent_ctx->mutex);

		perf_unpin_context(parent_ctx);

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