linux-kernel - [PATCH 2/2] perf: Disallow aux

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Message-Id: <20191030134731.5437-3-alexander.shishkin@linux.intel.com>
Date:   Wed, 30 Oct 2019 15:47:31 +0200
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:     Arnaldo Carvalho de Melo <acme@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: [PATCH 2/2] perf: Disallow aux_output for kernel events

Commit

  ab43762ef0109 ("perf: Allow normal events to output AUX data")

added 'aux_output' bit to the attribute structure, which relies on AUX
events and grouping, neither of which is supported for the kernel events.
This notwithstanding, attempts have been made to use it in the kernel
code, suggesting the necessity of an explicit hard -EINVAL.

Fix this by rejecting attributes with aux_output set for kernel events.

Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
---
 kernel/events/core.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index d2f16546a2ab..d31cf601c710 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -11415,6 +11415,13 @@ perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu,
 	struct perf_event *event;
 	int err;
 
+	/*
+	 * Grouping is not supported for kernel events, neither is 'AUX',
+	 * make sure the caller's intentions are adjusted.
+	 */
+	if (attr->aux_output)
+		return -EINVAL;
+
 	event = perf_event_alloc(attr, cpu, task, NULL, NULL,
 				 overflow_handler, context, -1);
 	if (IS_ERR(event)) {
-- 
2.23.0