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SubjectRe: [PATCH v2 10/10] powerpc/32s: Implement Kernel Userspace Access Protection
Date
Christophe Leroy <christophe.leroy@c-s.fr> writes:
> diff --git a/arch/powerpc/include/asm/book3s/32/kup.h b/arch/powerpc/include/asm/book3s/32/kup.h
> index 5f97c742ca71..b3560b2de435 100644
> --- a/arch/powerpc/include/asm/book3s/32/kup.h
> +++ b/arch/powerpc/include/asm/book3s/32/kup.h
> @@ -37,6 +37,113 @@
...
> +
> +static inline void allow_user_access(void __user *to, const void __user *from, u32 size)
> +{
> + u32 addr = (__force u32)to;
> + u32 end = min(addr + size, TASK_SIZE);
> +
> + if (!addr || addr >= TASK_SIZE || !size)
> + return;
> +
> + current->thread.kuap = (addr & 0xf0000000) | ((((end - 1) >> 28) + 1) & 0xf);
> + kuap_update_sr(mfsrin(addr) & ~SR_KS, addr, end); /* Clear Ks */
> +}

When rebasing on my v6 I changed the above to:

static inline void allow_user_access(void __user *to, const void __user *from, u32 size)
{
u32 addr, end;

if (__builtin_constant_p(to) && to == NULL)
return;

addr = (__force u32)to;

if (!addr || addr >= TASK_SIZE || !size)
return;

end = min(addr + size, TASK_SIZE);
current->thread.kuap = (addr & 0xf0000000) | ((((end - 1) >> 28) + 1) & 0xf);
kuap_update_sr(mfsrin(addr) & ~SR_KS, addr, end); /* Clear Ks */
}

Which I think achieves the same result. It does boot :)

> +
> +static inline void prevent_user_access(void __user *to, const void __user *from, u32 size)
> +{
> + u32 addr = (__force u32)to;
> + u32 end = min(addr + size, TASK_SIZE);
> +
> + if (!addr || addr >= TASK_SIZE || !size)
> + return;
> +
> + current->thread.kuap = 0;
> + kuap_update_sr(mfsrin(addr) | SR_KS, addr, end); /* set Ks */
> +}
> +
> +static inline void allow_read_from_user(const void __user *from, unsigned long size)
> +{
> +}

And I dropped that.

cheers

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