linux-kernel - [PATCH 1/2] perf ioctl: Add check for the sample

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Message-Id: <20190511024217.4013-1-ravi.bangoria@linux.ibm.com>
Date:   Sat, 11 May 2019 08:12:16 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
To:     peterz@...radead.org, jolsa@...hat.com, mpe@...erman.id.au,
        maddy@...ux.vnet.ibm.com
Cc:     acme@...nel.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Subject: [PATCH 1/2] perf ioctl: Add check for the sample_period value

Add a check for sample_period value sent from userspace. Negative
value does not make sense. And in powerpc arch code this could cause
a recursive PMI leading to a hang (reported when running perf-fuzzer).

Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
---
 kernel/events/core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index abbd4b3b96c2..e44c90378940 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5005,6 +5005,9 @@ static int perf_event_period(struct perf_event *event, u64 __user *arg)
 	if (perf_event_check_period(event, value))
 		return -EINVAL;
 
+	if (!event->attr.freq && (value & (1ULL << 63)))
+		return -EINVAL;
+
 	event_function_call(event, __perf_event_period, &value);
 
 	return 0;
-- 
2.20.1