Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCH] x86/iopl: Fake iopl(3) CLI/STI usage | Date | Fri, 17 Sep 2021 12:40:43 +0200 |
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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>
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