linux-kernel - Re: [PATCH] drivers: perf: Check find_first

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Message-ID: <CAOnJCUK+guaWFsefnU80tfedkBU9hNWtOX9LqbXVT4JhEUf6Rw@mail.gmail.com>
Date:   Thu, 9 Nov 2023 08:39:13 -0800
From:   Atish Patra <atishp@...shpatra.org>
To:     Alexandre Ghiti <alexghiti@...osinc.com>
Cc:     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: Re: [PATCH] drivers: perf: Check find_first_bit() return value

On Thu, Nov 9, 2023 at 12:21 AM Alexandre Ghiti <alexghiti@...osinc.com> wrote:
>
> We must check the return value of find_first_bit() before using the
> return value as an index array since it happens to overflow the array
> and then panic:
>
> [  107.318430] Kernel BUG [#1]
> [  107.319434] CPU: 3 PID: 1238 Comm: kill Tainted: G            E      6.6.0-rc6ubuntu-defconfig #2
> [  107.319465] Hardware name: riscv-virtio,qemu (DT)
> [  107.319551] epc : pmu_sbi_ovf_handler+0x3a4/0x3ae
> [  107.319840]  ra : pmu_sbi_ovf_handler+0x52/0x3ae
> [  107.319868] epc : ffffffff80a0a77c ra : ffffffff80a0a42a sp : ffffaf83fecda350
> [  107.319884]  gp : ffffffff823961a8 tp : ffffaf8083db1dc0 t0 : ffffaf83fecda480
> [  107.319899]  t1 : ffffffff80cafe62 t2 : 000000000000ff00 s0 : ffffaf83fecda520
> [  107.319921]  s1 : ffffaf83fecda380 a0 : 00000018fca29df0 a1 : ffffffffffffffff
> [  107.319936]  a2 : 0000000001073734 a3 : 0000000000000004 a4 : 0000000000000000
> [  107.319951]  a5 : 0000000000000040 a6 : 000000001d1c8774 a7 : 0000000000504d55
> [  107.319965]  s2 : ffffffff82451f10 s3 : ffffffff82724e70 s4 : 000000000000003f
> [  107.319980]  s5 : 0000000000000011 s6 : ffffaf8083db27c0 s7 : 0000000000000000
> [  107.319995]  s8 : 0000000000000001 s9 : 00007fffb45d6558 s10: 00007fffb45d81a0
> [  107.320009]  s11: ffffaf7ffff60000 t3 : 0000000000000004 t4 : 0000000000000000
> [  107.320023]  t5 : ffffaf7f80000000 t6 : ffffaf8000000000
> [  107.320037] status: 0000000200000100 badaddr: 0000000000000000 cause: 0000000000000003
> [  107.320081] [<ffffffff80a0a77c>] pmu_sbi_ovf_handler+0x3a4/0x3ae
> [  107.320112] [<ffffffff800b42d0>] handle_percpu_devid_irq+0x9e/0x1a0
> [  107.320131] [<ffffffff800ad92c>] generic_handle_domain_irq+0x28/0x36
> [  107.320148] [<ffffffff8065f9f8>] riscv_intc_irq+0x36/0x4e
> [  107.320166] [<ffffffff80caf4a0>] handle_riscv_irq+0x54/0x86
> [  107.320189] [<ffffffff80cb0036>] do_irq+0x64/0x96
> [  107.320271] Code: 85a6 855e b097 ff7f 80e7 9220 b709 9002 4501 bbd9 (9002) 6097
> [  107.320585] ---[ end trace 0000000000000000 ]---
> [  107.320704] Kernel panic - not syncing: Fatal exception in interrupt
> [  107.320775] SMP: stopping secondary CPUs
> [  107.321219] Kernel Offset: 0x0 from 0xffffffff80000000
> [  107.333051] ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---
>
> Fixes: 4905ec2fb7e6 ("RISC-V: Add sscofpmf extension support")
> Signed-off-by: Alexandre Ghiti <alexghiti@...osinc.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 439da49dd0a9..93d729213140 100644
> --- a/drivers/perf/riscv_pmu_sbi.c
> +++ b/drivers/perf/riscv_pmu_sbi.c
> @@ -687,6 +687,11 @@ static irqreturn_t pmu_sbi_ovf_handler(int irq, void *dev)
>
>         /* Firmware counter don't support overflow yet */
>         fidx = find_first_bit(cpu_hw_evt->used_hw_ctrs, RISCV_MAX_COUNTERS);
> +       if (fidx == RISCV_MAX_COUNTERS) {
> +               csr_clear(CSR_SIP, BIT(riscv_pmu_irq_num));
> +               return IRQ_NONE;
> +       }
> +
>         event = cpu_hw_evt->events[fidx];
>         if (!event) {
>                 csr_clear(CSR_SIP, BIT(riscv_pmu_irq_num));
> --
> 2.39.2
>


Reviewed-by: Atish Patra <atishp@...osinc.com>

-- 
Regards,
Atish