linux-kernel - Re: [PATCH 3/8] x86, fpu: kill save_init_fpu(), change math_error() to use unlazy

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:	Mon, 16 Feb 2015 16:30:50 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Borislav Petkov <bp@...en8.de>, oleg@...hat.com
CC:	dave.hansen@...ux.intel.com, sbsiddha@...il.com,
	luto@...capital.net, tglx@...utronix.de, mingo@...nel.org,
	hpa@...or.com, fenghua.yu@...el.com, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/8] x86, fpu: kill save_init_fpu(), change math_error()
 to use unlazy_fpu()

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 02/16/2015 04:09 PM, Borislav Petkov wrote:
> On Fri, Feb 06, 2015 at 03:02:00PM -0500, riel@...hat.com wrote:
>> From: Oleg Nesterov <oleg@...hat.com>

>> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c 
>> index fb4cb6adf225..51c465846f06 100644 ---
>> a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -663,7
>> +663,7 @@ static void math_error(struct pt_regs *regs, int
>> error_code, int trapnr) /* * Save the info for the exception
>> handler and clear the error. */ -	save_init_fpu(task); +
>> unlazy_fpu(task);
> 
> Do I see it correctly that even with this there's a not-so-small
> hole *after* conditional_sti() and *before* unlazy_fpu() where
> caller can still get preempted?

That's ok, the context switch will save the register contents
to memory in that case. At that point unlazy_fpu will potentially
do nothing, and the task will process the FPU context that was
saved to memory previously.

- -- 
All rights reversed
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1

iQEcBAEBAgAGBQJU4mGKAAoJEM553pKExN6DHoAH/1R3Pak5bZrvnCEBd3lp9/uD
bqtms5VjiWNNhlG0Hpob0eS71p8fO9La8+hPwFQJdK9yZ2lwvrDEXMCMGOG1P8by
HHbtxS74tUIm49qlIIUNxoiI+HMDnOQNhYv9dA4VdTMcY//2Asr6g4LM3wFH+f1q
tZJ5CU5/f0g2SCtTEzXxZDQdlqgpGXpvcGVymENe45uzn5ZYgcbCAiix+Dy5SiCw
+GjURoRW07iRSvK48w8vTVstTwl2WKgHpWEGVGhL1RyJY6aMIft3b4FH1jUrhVVJ
w3ncQAptA2ry/anU/6A2aTrZ646ebJuYejhF99gwTucolJ3netdX7xohOaFEpSc=
=/rU9
-----END PGP SIGNATURE-----
--
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/