NAK Re: [PATCH] UBUNTU: SAUCE: RISC-V: prevent sbi_send_cpumask_ipi race with ftrace

[Dimitri John Ledkov]

see the v2 patch with BugLink, Tested-By, SOB headers and comment
which series this patch is applicable to.

On Wed, Aug 11, 2021 at 10:21 AM Dimitri John Ledkov
<dimitri.ledkov at canonical.com> wrote:
>
> From: Thadeu Lima de Souza Cascardo <cascardo at canonical.com>
>
> ftrace will patch instructions in sbi_send_cpumask_ipi, which is going to
> be used by flush_icache_range, leading to potential races and crashes like
> this:
>
> [    0.000000] ftrace: allocating 38893 entries in 152 pages
> [    0.000000] Oops - illegal instruction [#1]
> [    0.000000] Modules linked in:
> [    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 5.11.0-1014-generic #14-Ubuntu
> [    0.000000] epc: ffffffe00000920e ra : ffffffe000009384 sp : ffffffe001803d30
> [    0.000000]  gp : ffffffe001a14240 tp : ffffffe00180f440 t0 : ffffffe07fe38000
> [    0.000000]  t1 : ffffffe0019cd338 t2 : 0000000000000000 s0 : ffffffe001803d70
> [    0.000000]  s1 : 0000000000000000 a0 : ffffffe0000095aa a1 : 0000000000000001
> [    0.000000]  a2 : 0000000000000002 a3 : 0000000000000000 a4 : 0000000000000000
> [    0.000000]  a5 : 0000000000000000 a6 : 0000000000000004 a7 : 0000000052464e43
> [    0.000000]  s2 : 0000000000000002 s3 : 0000000000000001 s4 : 0000000000000000
> [    0.000000]  s5 : 0000000000000000 s6 : 0000000000000000 s7 : 0000000000000000
> [    0.000000]  s8 : ffffffe001a170c0 s9 : 0000000000000001 s10: 0000000000000001
> [    0.000000]  s11: 00000000fffcc5d0 t3 : 0000000000000068 t4 : 000000000000000b
> [    0.000000]  t5 : ffffffe0019cd3e0 t6 : ffffffe001803cd8
> [    0.000000] status: 0000000200000100 badaddr: 000000000513f187 cause: 0000000000000002
> [    0.000000] ---[ end trace f67eb9af4d8d492b ]---
> [    0.000000] Kernel panic - not syncing: Attempted to kill the idle task!
> [    0.000000] ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]---
>
> Where ffffffe00000920e lies in the middle of sbi_send_cpumask_ipi.
>
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo at canonical.com>
> ---
>  arch/riscv/kernel/sbi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
> index b8f82c73deb7..9f85f0656f71 100644
> --- a/arch/riscv/kernel/sbi.c
> +++ b/arch/riscv/kernel/sbi.c
> @@ -562,7 +562,7 @@ long sbi_get_impid(void)
>         return __sbi_base_ecall(SBI_EXT_BASE_GET_MIMPID);
>  }
>
> -static void sbi_send_cpumask_ipi(const struct cpumask *target)
> +static void notrace sbi_send_cpumask_ipi(const struct cpumask *target)
>  {
>         struct cpumask hartid_mask;
>
> --
> 2.30.2
>


-- 
Regards,

Dimitri.