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

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Message-ID: <202408221712.DC796105C@keescook>
Date: Thu, 22 Aug 2024 17:12:37 -0700
From: Kees Cook <kees@...nel.org>
To: Dave Hansen <dave.hansen@...el.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
	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 Thu, Jul 11, 2024 at 02:01:53PM -0700, Dave Hansen wrote:
> 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>

Ping. I can take it via the hardening tree if you want, though?

-- 
Kees Cook