From: Thomas Gleixner <tglx@linutronix.de>
To: Peter Zijlstra <peterz@infradead.org>, Ondrej Zary <linux@zary.sk>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] x86/iopl: Fake iopl(3) CLI/STI usage
Date: Fri, 17 Sep 2021 12:40:43 +0200 [thread overview]
Message-ID: <87pmt78oyc.ffs@tglx> (raw)
In-Reply-To: <YURdxNpH8YNQZQT7@hirez.programming.kicks-ass.net>
On Fri, Sep 17 2021 at 11:20, Peter Zijlstra wrote:
> Subject: x86/iopl: Fake iopl(3) CLI/STI usage
> From: Peter Zijlstra <peterz@infradead.org>
> Date: Thu, 16 Sep 2021 23:05:09 +0200
>
> 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>
next prev parent reply other threads:[~2021-09-17 10:40 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 [this message]
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
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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