linux-kernel - Re: ioperm is preserved across fork and execve, but iopl is not

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Message-ID: <20150511221125.177336d6@lxorguk.ukuu.org.uk>
Date:	Mon, 11 May 2015 22:11:25 +0100
From:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
To:	Alex Henrie <alexhenrie24@...il.com>
Cc:	Kees Cook <keescook@...omium.org>,
	"H. Peter Anvin" <hpa@...or.com>, Doug Johnson <dougvj@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Tyler Hicks <tyhicks@...onical.com>,
	Al Viro <viro@...iv.linux.org.uk>, linux-kernel@...r.kernel.org
Subject: Re: ioperm is preserved across fork and execve, but iopl is not

> As recently as October 2012, 32-bit Linux kernels preserved both iopl
> and ioperm across fork and execve, but the behavior of iopl changed
> with this commit:
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/arch/x86/kernel/process_32.c?id=6783eaa2e1253fbcbe2c2f6bb4c843abf1343caf

Missed this thread initially. That perhaps does argue for it being safer
to put back.

> And the man page for iopl continues to state "permissions are
> inherited by fork and execve": http://linux.die.net/man/2/iopl
> 
> A test program demonstrating the problem is attached

Is there a real world use case ?

Alan
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