linux-kernel - Re: [RFC PATCH] x86/cpu: Fix MSR value truncation issue

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: <CALCETrXpjxHFszxDYdT=iZo8O-x7eNy_FBePSkqTjVzZfVT-fg@mail.gmail.com>
Date:	Fri, 30 Oct 2015 11:59:39 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Borislav Petkov <bp@...en8.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andy Lutomirski <luto@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC PATCH] x86/cpu: Fix MSR value truncation issue

On Fri, Oct 30, 2015 at 10:28 AM, Borislav Petkov <bp@...en8.de> wrote:
> From: Borislav Petkov <bp@...e.de>
>
> So sparse rightfully complains that the u64 MSR value we're writing into
> the STAR MSR, i.e. 0xc0000081, is being truncated:
>
> ./arch/x86/include/asm/msr.h:193:36: warning: cast truncates bits from constant value (23001000000000 becomes 0)

Is this with or without:

commit 47edb65178cb7056c2eea0b6c41a7d8c84547192
Author: Andy Lutomirski <luto@...nel.org>
Date:   Thu Jul 23 12:14:40 2015 -0700

    x86/asm/msr: Make wrmsrl() a function

If that patch is applied, then I think that gcc is just being dumb and
that we should consider tweaking wrmsrl to avoid generating the
warning.  Maybe change (u32)val to (u32)(val & 0xffffffffull)?

I don't see why we should uglify the caller when the problem is some
combination of gcc and the wrmsrl implementation.

--Andy
--
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/