linux-kernel - [PATCH v2] perf ioctl: Add check for the sample

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Date:   Tue,  4 Jun 2019 09:59:53 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
To:     mpe@...erman.id.au, peterz@...radead.org
Cc:     jolsa@...hat.com, maddy@...ux.vnet.ibm.com, acme@...nel.org,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Subject: [PATCH v2] perf ioctl: Add check for the sample_period value

perf_event_open() limits the sample_period to 63 bits. See
commit 0819b2e30ccb ("perf: Limit perf_event_attr::sample_period
to 63 bits"). Make ioctl() consistent with it.

Also on powerpc, negative sample_period could cause a recursive
PMIs 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