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From: Ondrej Zary <linux@zary.sk>
To: linux-kernel@vger.kernel.org
Cc: linux-tip-commits@vger.kernel.org,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	x86@kernel.org
Subject: Re: [tip: x86/core] x86/iopl: Fake iopl(3) CLI/STI usage
Date: Tue, 21 Sep 2021 13:09:26 +0200	[thread overview]
Message-ID: <202109211309.26518.linux@zary.sk> (raw)
In-Reply-To: <163220928593.25758.16098239507716851071.tip-bot2@tip-bot2>

On Tuesday 21 September 2021, tip-bot2 for Peter Zijlstra wrote:
> The following commit has been merged into the x86/core branch of tip:
> 
> Commit-ID:     32e1ae626f295152d1fc9a3375214133cbe62878
> Gitweb:        https://git.kernel.org/tip/32e1ae626f295152d1fc9a3375214133cbe62878
> Author:        Peter Zijlstra <peterz@infradead.org>
> AuthorDate:    Fri, 17 Sep 2021 11:20:04 +02:00
> Committer:     Peter Zijlstra <peterz@infradead.org>
> CommitterDate: Sat, 18 Sep 2021 12:18:32 +02:00
> 
> x86/iopl: Fake iopl(3) CLI/STI usage
> 
> Since commit c8137ace5638 ("x86/iopl: Restrict iopl() permission
> scope") it's possible to emulate iopl(3) using ioperm(), except for
> the CLI/STI usage.
> 
> Userspace CLI/STI usage is very dubious (read broken), since any
> exception taken during that window can lead to rescheduling anyway (or
> worse). The IOPL(2) manpage even states that usage of CLI/STI is highly
> discouraged and might even crash the system.
> 
> Of course, that won't stop people and HP has the dubious honour of
> being the first vendor to be found using this in their hp-health
> package.
> 
> In order to enable this 'software' to still 'work', have the #GP treat
> the CLI/STI instructions as NOPs when iopl(3). Warn the user that
> their program is doing dubious things.
> 
> Fixes: a24ca9976843 ("x86/iopl: Remove legacy IOPL option")
> Reported-by: Ondrej Zary <linux@zary.sk>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
> Link: https://lkml.kernel.org/r/20210918090641.GD5106@worktop.programming.kicks-ass.net

Could this be backported to 5.10 kernel so it can get into the recently released Debian 11?

-- 
Ondrej Zary

  reply	other threads:[~2021-09-21 11:09 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-15 12:23 IOPL emulation breaks hpasmd (hp-health) needed by HP DL380 G4 servers Ondrej Zary
2021-09-16 17:09 ` Thomas Gleixner
2021-09-16 20:27   ` Ondrej Zary
2021-09-16 21:05     ` Peter Zijlstra
2021-09-17  8:11       ` Ondrej Zary
2021-09-17  9:20         ` [PATCH] x86/iopl: Fake iopl(3) CLI/STI usage Peter Zijlstra
2021-09-17 10:29           ` Ondrej Zary
2021-09-17 11:54             ` Peter Zijlstra
2021-09-17 12:33               ` Thomas Gleixner
2021-09-17 12:54                 ` Ondrej Zary
2021-09-17 10:40           ` Thomas Gleixner
2021-09-17 22:23           ` Linus Torvalds
2021-09-17 22:24             ` Linus Torvalds
2021-09-18  7:05               ` Peter Zijlstra
2021-09-18  9:06                 ` Peter Zijlstra
2021-09-18 15:53                   ` Ondrej Zary
2021-09-18 16:35                   ` Linus Torvalds
2021-09-21  7:28                   ` [tip: x86/core] " tip-bot2 for Peter Zijlstra
2021-09-21 11:09                     ` Ondrej Zary [this message]
2021-09-21 12:00                       ` Peter Zijlstra
2021-09-21 17:31                         ` Ondrej Zary
2021-09-21 12:41                   ` tip-bot2 for Peter Zijlstra
2021-09-21 21:01                 ` [PATCH] " Andy Lutomirski
2021-09-16 21:25     ` IOPL emulation breaks hpasmd (hp-health) needed by HP DL380 G4 servers Thomas Gleixner

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