Re: Fwd: ioperm is preserved across fork and execve, but iopl is not

[H. Peter Anvin]

On 05/11/2015 01:49 PM, Alex Henrie wrote:
> 
> The ioperm and iopl calls are both used to grant a process permission
> to access I/O devices directly. iopl(3) is equivalent to ioperm(0,
> 0xFFFF, 1). However, permissions granted through ioperm are preserved
> across fork and execve, and permissions granted through iopl are not.
> This makes no sense: The two calls do the same thing, so there is no
> security benefit to dropping one on fork or execve but not the other.
> 

They don't, in fact.  An iopl(3) process is allowed to disable
interrupts in user space, which an ioperm() process is not.

This is a HUGE deal.  This really makes me wonder if iopl(3) should be
allowed at all, or if we should just intercept it and treat it as ioperm().
	
	-hpa


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