[PATCH] riscv/mm: Add handling for VM_FAULT_SIGSEGV in mm_fault_error()

[Alexandre Ghiti]

Hi Zhe,

On Wed, Jul 31, 2024 at 5:26 AM Zhe Qiao <qiaozhe at iscas.ac.cn> wrote:
>
> Add processing for VM_CAULT_SIGSEGV to mm_fault_error () to avoid
> direct execution of BUG().

Sorry to bother you again, but since there is a typo
(s/VM_CAULT_SIGSEGV/VM_FAULT_SIGSEGV), do you mind rephrasing the
commit log like this (or similar)?

"Handle VM_FAULT_SIGSEGV in the page fault path so that we correctly
kill the process and we don't BUG() the kernel."

>
> Fixes: 07037db5d479 ("RISC-V: Paging and MMU")
> Signed-off-by: Zhe Qiao <qiaozhe at iscas.ac.cn>
> ---
>  arch/riscv/mm/fault.c | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
> index 5224f3733802..a9f2b4af8f3f 100644
> --- a/arch/riscv/mm/fault.c
> +++ b/arch/riscv/mm/fault.c
> @@ -61,26 +61,27 @@ static inline void no_context(struct pt_regs *regs, unsigned long addr)
>
>  static inline void mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_fault_t fault)
>  {
> +       if (!user_mode(regs)) {
> +               no_context(regs, addr);
> +               return;
> +       }
> +
>         if (fault & VM_FAULT_OOM) {
>                 /*
>                  * We ran out of memory, call the OOM killer, and return the userspace
>                  * (which will retry the fault, or kill us if we got oom-killed).
>                  */
> -               if (!user_mode(regs)) {
> -                       no_context(regs, addr);
> -                       return;
> -               }
>                 pagefault_out_of_memory();
>                 return;
>         } else if (fault & (VM_FAULT_SIGBUS | VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE)) {
>                 /* Kernel mode? Handle exceptions or die */
> -               if (!user_mode(regs)) {
> -                       no_context(regs, addr);
> -                       return;
> -               }
>                 do_trap(regs, SIGBUS, BUS_ADRERR, addr);
>                 return;
> +       } else if (fault & VM_FAULT_SIGSEGV) {
> +               do_trap(regs, SIGSEGV, SEGV_MAPERR, addr);
> +               return;
>         }
> +
>         BUG();
>  }
>
> --
> 2.43.0
>

That's a very good catch, good job! You can add:

Reviewed-by: Alexandre Ghiti <alexghiti at rivosinc.com>

Thanks,

Alex