linux-kernel - Re: [PATCH] x86/syscall: Avoid memcpy() for ia32 syscall_get

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Message-ID: <842a88e0-90ae-48be-91c9-8a7c3a8359a9@intel.com>
Date: Thu, 11 Jul 2024 14:01:53 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Kees Cook <kees@...nel.org>, Thomas Gleixner <tglx@...utronix.de>
Cc: Mirsad Todorovac <mtodorovac69@...il.com>, Ingo Molnar
 <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
 Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
 "H. Peter Anvin" <hpa@...or.com>,
 Daniel Sneddon <daniel.sneddon@...ux.intel.com>,
 Arnd Bergmann <arnd@...db.de>, Brian Gerst <brgerst@...il.com>,
 Josh Poimboeuf <jpoimboe@...nel.org>,
 Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
 Peter Collingbourne <pcc@...gle.com>, linux-kernel@...r.kernel.org,
 linux-hardening@...r.kernel.org
Subject: Re: [PATCH] x86/syscall: Avoid memcpy() for ia32
 syscall_get_arguments()

On 7/8/24 13:22, Kees Cook wrote:
...
> diff --git a/arch/x86/include/asm/syscall.h b/arch/x86/include/asm/syscall.h
> index 2fc7bc3863ff..7c488ff0c764 100644
> --- a/arch/x86/include/asm/syscall.h
> +++ b/arch/x86/include/asm/syscall.h
> @@ -82,7 +82,12 @@ static inline void syscall_get_arguments(struct task_struct *task,
>  					 struct pt_regs *regs,
>  					 unsigned long *args)
>  {
> -	memcpy(args, &regs->bx, 6 * sizeof(args[0]));
> +	args[0] = regs->bx;
> +	args[1] = regs->cx;
> +	args[2] = regs->dx;
> +	args[3] = regs->si;
> +	args[4] = regs->di;
> +	args[5] = regs->bp;
>  }
>  

Yeah, that's much less magic.  I'll stick this in the queue to go in to
the tree in a few weeks.

Acked-by: Dave Hansen <dave.hansen@...ux.intel.com>