linux-kernel - Re: Segfault in fbcmap.c => Compiler bug?

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] [day] [month] [year] [list]

Message-ID: <20081211110616.72f2d937@hskinnemoen-d830>
Date:	Thu, 11 Dec 2008 11:06:16 +0100
From:	Haavard Skinnemoen <haavard.skinnemoen@...el.com>
To:	Alex Raimondi <mailinglist@...omico.ch>
Cc:	kernel@...32linux.org, linux-kernel@...r.kernel.org
Subject: Re: Segfault in fbcmap.c => Compiler bug?

Alex Raimondi wrote:
> 			if (transp) 
> 				htransp = *transp++;
> 
> 
> The segfault happens at the if (transp) statment.
> 
> Now to the strange thing, which makes me guess this may be a problem related to a compiler bug:
> 
> When I change the if statment to:
> 
> 			if (transp) {
> 				printk("e\n");
> 				htransp = *transp++;
> 			}

Yeah, as HC pointed out, this is caused by a buggy toolchain. Although
I don't have any disassembly to back it up, I'm willing to bet that it
will show an unconditional load followed by a conditional mov. The
printk() implies a barrier, which will prevent the faulty optimization
from happening.

Haavard
--
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/