Add processing for VM_CAULT_SIGSEGV to mm_fault_error () to avoid
direct execution of BUG().

Fixes: 07037db5d479 ("RISC-V: Paging and MMU")
Signed-off-by: Zhe Qiao <qiaozhe@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

Hi Zhe,

On Wed, Jul 31, 2024 at 5:26 AM Zhe Qiao <qiaozhe@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@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@rivosinc.com>

Thanks,

Alex