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@yadro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20230505072058.1049732-1-v.v.mitrofanov@yadro.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/drivers/perf/riscv_pmu_sbi.c b/drivers/perf/riscv_pmu_sbi.c
index 0bc4912..4163ff5 100644 (file)
--- a/drivers/perf/riscv_pmu_sbi.c
+++ b/drivers/perf/riscv_pmu_sbi.c
@@ -855,6 +855,12 @@ static int pmu_sbi_device_probe(struct platform_device *pdev)
                goto out_free;
        }
 
+       /* It is possible to get from SBI more than max number of counters */
+       if (num_counters > RISCV_MAX_COUNTERS) {
+               num_counters = RISCV_MAX_COUNTERS;
+               pr_info("SBI returned more than maximum number of counters. Limiting the number of counters to %d\n", num_counters);
+       }
+
        /* cache all the information about counters now */
        if (pmu_sbi_get_ctrinfo(num_counters, &cmask))
                goto out_free;