linux-kernel - Re: [tip:x86/asm] x86-64, copy_user: Remove zero byte check before copy user buffer.

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]

Date:	Wed, 20 Nov 2013 13:44:16 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-tip-commits@...r.kernel.org,
	Fenghua Yu <fenghua.yu@...el.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [tip:x86/asm] x86-64, copy_user: Remove zero byte check before
 copy user buffer.

On Wed, Nov 20, 2013 at 12:36 PM, H. Peter Anvin <hpa@...or.com> wrote:
>
> That being said, "lea (%rdx,%rcx,8),%ecx" (leal, as opposed to leaq) is
> a perfectly legitimate instruction and actually one byte shorter.  The
> big question is if some broken version of gas will choke on it.

At least gcc-4.8.2 generates that instruction (try multiplying an
integer value by 9), so I guess gas will be happy. Except gcc uses
"leal", so to be safe..

              Linus
--
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/