linux-kernel - Re: [PATCH] Introduce compat_u64 and compat

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]

Date:	Fri, 15 Jun 2007 13:47:08 +0100
From:	David Woodhouse <dwmw2@...radead.org>
To:	Andi Kleen <ak@...e.de>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Dave Airlie <airlied@...ux.ie>, linux-arch@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] Introduce compat_u64 and compat_s64 types

On Fri, 2007-06-15 at 14:40 +0200, Andi Kleen wrote:
> > That is broken on all non-x86 architectures, 

> It cannot be broken, it just might be somewhat slower 

No, Andi. It's broken.

We're speaking of a 32-bit ioctl compat routine. I would say it's more
than 'convention' that the structure used by the compat_ioctl routine
actually matches the 'real' structure as it gets laid out on the 32-bit
architecture.

The 'real' structure as used by the 32-bit userspace does not have the
'packed' attribute. Thus the u64 member of the structure is aligned to 8
bytes on _all_ relevant 32-bit architectures except for i386.

By adding 'packed' in the compat_ioctl routine, you cause it to expect a
structure which does not match what userspace is using, for all non-x86
architectures. That's kind of not very compatible. I call that 'broken'.

-- 
dwmw2

-
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/