[PATCH 1/1] perf_event: add check for group_list if the parent isn't counted

[Liming Wang]

If the parent has no entry in group_list, child_ctx will not be
allocated, which will lead dereference of a NULL child_ctx.

Signed-off-by: Liming Wang <liming.wang@xxxxxxxxxxxxx>
---
 kernel/perf_event.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 5b987b4..3664c4b 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -5126,6 +5126,8 @@ int perf_event_init_task(struct task_struct *child)
 	 */
 	mutex_lock(&parent_ctx->mutex);
 
+	if (list_empty(&parent_ctx->group_list))
+		goto exit;
 	/*
 	 * We dont have to disable NMIs - we are only looking at
 	 * the list, not manipulating it:
-- 
1.6.0.3

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