Re: [PATCH 26/26] x86, pkeys: Documentation

[Dave Hansen]

On 10/01/2015 03:48 PM, Linus Torvalds wrote:
> On Thu, Oct 1, 2015 at 6:33 PM, Dave Hansen <dave@xxxxxxxx> wrote:
>>
>> Here it is in a quite fugly form (well, it's not opt-in).  Init crashes
>> if I boot with this, though.
>>
>> I'll see if I can turn it in to a bit more of an opt-in and see what's
>> actually going wrong.
...
> That said, I don't understand your patch. Why check PROT_WRITE? We've
> had :"execute but not write" forever. It's "execute and not *read*"
> that is interesting.

I was thinking that almost anybody doing a PROT_WRITE|PROT_EXEC really
*is* going to write to it so they'll notice pretty fast if we completely
deny them access to it.

Also, a quick ftrace showed that most mmap() callers that set PROT_EXEC
also set PROT_READ.  I'm just assuming that folks are setting PROT_READ
but aren't _really_ going to read it, so we can safely deny them all
access other than exec.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/