Re: [PATCH v2 06/15] powerpc/align: Don't use __get_user_instr() on kernel addresses

[Daniel Axtens]

Christophe Leroy  writes:

> In the old days, when we didn't have kernel userspace access
> protection and had set_fs(), it was wise to use __get_user()
> and friends to read kernel memory.
>
> Nowadays, get_user() is granting userspace access and is exclusively
> for userspace access.
>
> In alignment exception handler, use probe_kernel_read_inst()
> instead of __get_user_instr() for reading instructions in kernel.
>
> This will allow to remove the is_kernel_addr() check in
> __get/put_user() in a following patch.
>

Looks good to me!

Reviewed-by: Daniel Axtens 

Kind regards,
Daniel

> Signed-off-by: Christophe Leroy 
> ---
>  arch/powerpc/kernel/align.c | 6 +-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/kernel/align.c b/arch/powerpc/kernel/align.c
> index c4d7b445b459..8d4c7af262e2 100644
> --- a/arch/powerpc/kernel/align.c
> +++ b/arch/powerpc/kernel/align.c
> @@ -310,7 +310,11 @@ int fix_alignment(struct pt_regs *regs)
>*/
>   CHECK_FULL_REGS(regs);
>  
> - if (unlikely(__get_user_instr(instr, (void __user *)regs->nip)))
> + if (is_kernel_addr(regs->nip))
> + r = probe_kernel_read_inst(, (void *)regs->nip);
> + else
> + r = __get_user_instr(instr, (void __user *)regs->nip);
> + if (unlikely(r))
>   return -EFAULT;
>   if ((regs->msr & MSR_LE) != (MSR_KERNEL & MSR_LE)) {
>   /* We don't handle PPC little-endian any more... */
> -- 
> 2.25.0

[PATCH v2 06/15] powerpc/align: Don't use __get_user_instr() on kernel addresses

[Christophe Leroy]

In the old days, when we didn't have kernel userspace access
protection and had set_fs(), it was wise to use __get_user()
and friends to read kernel memory.

Nowadays, get_user() is granting userspace access and is exclusively
for userspace access.

In alignment exception handler, use probe_kernel_read_inst()
instead of __get_user_instr() for reading instructions in kernel.

This will allow to remove the is_kernel_addr() check in
__get/put_user() in a following patch.

Signed-off-by: Christophe Leroy 
---
 arch/powerpc/kernel/align.c | 6 +-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/align.c b/arch/powerpc/kernel/align.c
index c4d7b445b459..8d4c7af262e2 100644
--- a/arch/powerpc/kernel/align.c
+++ b/arch/powerpc/kernel/align.c
@@ -310,7 +310,11 @@ int fix_alignment(struct pt_regs *regs)
 */
CHECK_FULL_REGS(regs);
 
-   if (unlikely(__get_user_instr(instr, (void __user *)regs->nip)))
+   if (is_kernel_addr(regs->nip))
+   r = probe_kernel_read_inst(, (void *)regs->nip);
+   else
+   r = __get_user_instr(instr, (void __user *)regs->nip);
+   if (unlikely(r))
return -EFAULT;
if ((regs->msr & MSR_LE) != (MSR_KERNEL & MSR_LE)) {
/* We don't handle PPC little-endian any more... */
-- 
2.25.0