linux-kernel - Re: [git pull] x86 fixes

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1206650939.24940.43.camel@brick>
Date:	Thu, 27 Mar 2008 13:48:59 -0700
From:	Harvey Harrison <harvey.harrison@...il.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [git pull] x86 fixes

On Thu, 2008-03-27 at 13:31 -0700, Linus Torvalds wrote:
> 
> On Thu, 27 Mar 2008, Ingo Molnar wrote:
> >
> > Ingo Molnar (1):
> >       x86: fix prefetch workaround
> ...
> > diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> > index fdc6674..c0c82bc 100644
> > --- a/arch/x86/mm/fault.c
> > +++ b/arch/x86/mm/fault.c
> > @@ -92,7 +92,8 @@ static int is_prefetch(struct pt_regs *regs, unsigned long addr,
> >  	unsigned char *max_instr;
> >  
> >  #ifdef CONFIG_X86_32
> > -	if (!(__supported_pte_mask & _PAGE_NX))
> > +	/* Catch an obscure case of prefetch inside an NX page: */
> > +	if ((__supported_pte_mask & _PAGE_NX) && (error_code & 16))
> >  		return 0;
> >  #endif
> 
> Ingo, this patch makes no sense.
> 
> Two reasons:
> 
>  - "error_code & 16" is senseless. Use PF_INSTR instead, which actually 
>    tells the reader something.
> 
>  - this piece of crap code is immediately followed by
> 
> 	/* If it was a exec fault on NX page, ignore */
> 	if (error_code & PF_INSTR)
> 		return 0;
> 
>    which uses that *right* and readable PF_INSTR #define, and also shows 
>    that the newly modified code is totally insane (ie: if the new code 
>    triggers, then it would have returned 0 later _anyway_)
> 
> So I think it's just crap. I think it's duplication from the merging of 
> the x86 code, and I think that the fact that the new code didn't use the 
> right #define helper means that people didn't see that it was crap.
> 
> I pulled it, but this needs some resolution. The code makes no sense. 
> Should that #ifdef and the code inside of it just be removed entirely?
> 

Sorry, this was my fault, I eliminated the ifdef within the X86_32 block
but didn't go further.  Think the below is correct:

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index c0c82bc..6f5df93 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -91,14 +91,8 @@ static int is_prefetch(struct pt_regs *regs, unsigned long addr,
 	int prefetch = 0;
 	unsigned char *max_instr;
 
-#ifdef CONFIG_X86_32
 	/* Catch an obscure case of prefetch inside an NX page: */
-	if ((__supported_pte_mask & _PAGE_NX) && (error_code & 16))
-		return 0;
-#endif
-
-	/* If it was a exec fault on NX page, ignore */
-	if (error_code & PF_INSTR)
+	if ((__supported_pte_mask & _PAGE_NX) && (error_code & PF_INSTR))
 		return 0;
 
 	instr = (unsigned char *)convert_ip_to_linear(current, regs);



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/