linux-kernel - Re: [PATCH] Alpha: Emulate unaligned LDx_L/STx

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: <CAHk-=whKa0-myNkpq2aMCQ=o7S+Sqj--TQEM8wfC9b2C04jidA@mail.gmail.com>
Date: Mon, 7 Apr 2025 17:34:44 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: "Maciej W. Rozycki" <macro@...am.me.uk>
Cc: Richard Henderson <richard.henderson@...aro.org>, Ivan Kokshaysky <ink@...een.parts>, 
	Matt Turner <mattst88@...il.com>, Arnd Bergmann <arnd@...db.de>, 
	John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>, Magnus Lindholm <linmag7@...il.com>, 
	"Paul E. McKenney" <paulmck@...nel.org>, Al Viro <viro@...iv.linux.org.uk>, 
	linux-alpha@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Alpha: Emulate unaligned LDx_L/STx_C for data consistency

On Mon, 7 Apr 2025 at 13:46, Maciej W. Rozycki <macro@...am.me.uk> wrote:
>
>  So unless I'm proved otherwise (e.g. that all such code paths are now
> gone from networking, which may or may not be the case: I saw IPX go but I
> can see AppleTalk still around; or that no sub-longword accesses are ever
> used in the relevant networking paths), I'm going to keep kernel emulation
> in v2, because what just used to be wrapped in an unaligned LDQ/STQ pair,
> which we trapped on and emulated, will now become an LDQ_L/STQ_C loop.
>
>  Do you happen to know what the situation is here?

I think networking ends up using 'get_unaligned()' properly for header
accesses these days for any of this.

If you don't, some architectures will literally silently give you
garbage back and not even fault.

Admittedly that's mainly some really broken old 32-bit ARM stuff and
hopefully it's all dead by now.

So unless you actually *see* the unaligned faults, I really think you
shouldn't emulate them.

And I'd like to know where they are if you do see them

             Linus