Commit e7cc4865 authored Mar 16, 2017 by Peter Zijlstra Committed by Ingo Molnar Mar 16, 2017

perf/core: Fix event inheritance on fork()



While hunting for clues to a use-after-free, Oleg spotted that
perf_event_init_context() can loose an error value with the result
that fork() can succeed even though we did not fully inherit the perf
event context.

Spotted-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: oleg@redhat.com
Cc: stable@vger.kernel.org
Fixes: 889ff015 ("perf/core: Split context's event group list into pinned and non-pinned lists")
Link: http://lkml.kernel.org/r/20170316125823.190342547@infradead.org


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent e552a838

kernel/events/core.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -10679,7 +10679,7 @@ 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;
		}

		/*
		@@ -10695,7 +10695,7 @@ 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;
		}

		raw_spin_lock_irqsave(&parent_ctx->lock, flags);
		@@ -10723,6 +10723,7 @@ static int perf_event_init_context(struct task_struct *child, int ctxn)
		}

		raw_spin_unlock_irqrestore(&parent_ctx->lock, flags);
		out_unlock:
		mutex_unlock(&parent_ctx->mutex);

		perf_unpin_context(parent_ctx);