Re: [PATCH] arm64: Make TSK_STACK_CANARY more accurate defined

[Guo Ren]

On 2020/7/14 äå4:37, Will Deacon wrote:
> On Mon, Jul 13, 2020 at 04:03:33AM +0000, guoren@xxxxxxxxxx wrote:
> > From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
> >
> > TSK_STACK_CANARY only used in arm64/Makefile with
> > CONFIG_STACKPROTECTOR_PER_TASK wrap. So use the same policy in
> > asm-offset.c.
> >
> > Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
> > Co-developed-by: Kees Cook <keescook@xxxxxxxxxxxx>
> > Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> > Cc: Will Deacon <will@xxxxxxxxxx>
> > ---
> >   arch/arm64/kernel/asm-offsets.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> > index 0577e21..37d5d3d 100644
> > --- a/arch/arm64/kernel/asm-offsets.c
> > +++ b/arch/arm64/kernel/asm-offsets.c
> > @@ -39,7 +39,7 @@ int main(void)
> >     DEFINE(TSK_TI_SCS_SP,		offsetof(struct task_struct, thread_info.scs_sp));
> >   #endif
> >     DEFINE(TSK_STACK,		offsetof(struct task_struct, stack));
> > -#ifdef CONFIG_STACKPROTECTOR
> > +#ifdef CONFIG_STACKPROTECTOR_PER_TASK
> >     DEFINE(TSK_STACK_CANARY,	offsetof(struct task_struct, stack_canary));
> >   #endif
> I don't think this really makese much sense. The 'stack_canary' field in
> 'struct task_struct' is defined as:
>
> #ifdef CONFIG_STACKPROTECTOR
>          /* Canary value for the -fstack-protector GCC feature: */
>          unsigned long                   stack_canary;
> #endif
>
> so I think it makes sense to follow that in asm-offsets.c
>
> Does the current code actually cause a problem?
No, I just want to know how arm64 reply, ref:
https://lore.kernel.org/linux-riscv/1594397998-10221-1-git-send-email-guoren@xxxxxxxxxx/T/#t

Best Regards
ÂGuo Ren