Re: [PATCH v2] x86: Preserve iopl on fork and execve

From: Arjan van de Ven
Date: Tue May 12 2015 - 11:24:44 EST

On Mon, May 11, 2015 at 11:40 PM, Ingo Molnar <mingo@xxxxxxxxxx> wrote:
> - Nothing actually broke that people cared about in the last 2.5
> years, thus this might be one of the (very very rare) cases where
> preserving a breakage is the right thing to do.

> - These syscalls are rarely used, and we could as well insist that
> every new context should have the permissions to (re-)acquire them
> and should actively seek them - instead of inheriting it to shells
> via system(), etc. The best strategy with dangerous APIs is to make
> it really, really explicit when they are used.

since nothing really broke and its a "nasty either way" regression
wise, picking the more secure path looks the most sane.

the most likely impact path is in the X world, where X normally gets
iopl type permissions (even thought it doesn't need
them anymore nowadays).. reverting this behavior would give all the
processes X spawns off those perms as well...

also the interesting question is:
can a process give up these perms?
otherwise it becomes a "once given, never gotten rid of" hell hole.
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