linux-kernel - Re: [PATCH 05/12] x86-64: Disable preemption when using TS

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: <4C81EB93.4090304@kernel.org>
Date:	Sat, 04 Sep 2010 09:47:47 +0300
From:	Pekka Enberg <penberg@...nel.org>
To:	Brian Gerst <brgerst@...il.com>
CC:	hpa@...or.com, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 05/12] x86-64: Disable preemption when using TS_USEDFPU

  On 4.9.2010 4.17, Brian Gerst wrote:
> Consolidates code and fixes the below race for 64-bit.
>
> commit 9fa2f37bfeb798728241cc4a19578ce6e4258f25
> Author: torvalds<torvalds>
> Date:   Tue Sep 2 07:37:25 2003 +0000
>
>      Be a lot more careful about TS_USEDFPU and preemption
>
>      We had some races where we testecd (or set) TS_USEDFPU together
>      with sequences that depended on the setting (like clearing or
>      setting the TS flag in %cr0) and we could be preempted in between,
>      which screws up the FPU state, since preemption will itself change
>      USEDFPU and the TS flag.
>
>      This makes it a lot more explicit: the "internal" low-level FPU
>      functions ("__xxxx_fpu()") all require preemption to be disabled,
>      and the exported "real" functions will make sure that is the case.
>
>      One case - in __switch_to() - was switched to the non-preempt-safe
>      internal version, since the scheduler itself has already disabled
>      preemption.
>
>      BKrev: 3f5448b5WRiQuyzAlbajs3qoQjSobw
>
> Signed-off-by: Brian Gerst<brgerst@...il.com>
Acked-by: Pekka Enberg <penberg@...nel.org>

--
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/