linux-kernel - [PATCH 1/1] perf: RISC-V: Limit the number of counters returned from SBI.

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Message-ID: <20230428110256.711352-2-v.v.mitrofanov@yadro.com>
Date:   Fri, 28 Apr 2023 11:02:56 +0000
From:   Viacheslav Mitrofanov <v.v.mitrofanov@...ro.com>
To:     unlisted-recipients:; (no To-header on input)
CC:     <linux@...ro.com>,
        Viacheslav Mitrofanov <v.v.mitrofanov@...ro.com>,
        "Atish Patra" <atishp@...shpatra.org>,
        Anup Patel <anup@...infault.org>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        <linux-riscv@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH 1/1] perf: RISC-V: Limit the number of counters returned from SBI.

Perf gets the number of supported counters from SBI. If it happens that
the number of returned counters more than RISCV_MAX_COUNTERS the code
trusts it. It does not lead to an immediate problem but can potentially
lead to it. Prevent getting more than RISCV_MAX_COUNTERS from SBI.

Signed-off-by: Viacheslav Mitrofanov <v.v.mitrofanov@...ro.com>
---
 drivers/perf/riscv_pmu_sbi.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/perf/riscv_pmu_sbi.c b/drivers/perf/riscv_pmu_sbi.c
index 70cb50fd41c2..0183bf911bfb 100644
--- a/drivers/perf/riscv_pmu_sbi.c
+++ b/drivers/perf/riscv_pmu_sbi.c
@@ -867,6 +867,11 @@ static int pmu_sbi_device_probe(struct platform_device *pdev)
 		pr_err("SBI PMU extension doesn't provide any counters\n");
 		goto out_free;
 	}
+	/* It is possible to get from SBI more than max number of counters */
+	if (num_counters > RISCV_MAX_COUNTERS) {
+		pr_warn("SBI returned more than maximum number of counters\n");
+		num_counters = RISCV_MAX_COUNTERS;
+	}
 
 	/* cache all the information about counters now */
 	if (pmu_sbi_get_ctrinfo(num_counters, &cmask))
-- 
2.37.2