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perf: Fix racy group access 

While looking at some fuzzer output I noticed that we do not hold any
locks on leader->ctx and therefore the sibling_list iteration is
unsafe.

Acquire the relevant ctx->mutex before calling into the pmu specific
code.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Link: http://lkml.kernel.org/r/20150225151639.GL5029@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2015-02-25 15:56:04 +01:00 committed by Ingo Molnar
parent 9332d250b4
commit ccd41c86ad
1 changed files with 11 additions and 0 deletions
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11
kernel/events/core.c
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@ -7036,12 +7036,23 @@ EXPORT_SYMBOL_GPL(perf_pmu_unregister);
static int perf_try_init_event(struct pmu *pmu, struct perf_event *event)
{
struct perf_event_context *ctx = NULL;
int ret;
if (!try_module_get(pmu->module))
return -ENODEV;
if (event->group_leader != event) {
ctx = perf_event_ctx_lock(event->group_leader);
BUG_ON(!ctx);
}
event->pmu = pmu;
ret = pmu->event_init(event);
if (ctx)
perf_event_ctx_unlock(event->group_leader, ctx);
if (ret)
module_put(pmu->module);