Re: 2.6.23 regression: accessing invalid mmap'ed memory from gdb causes unkillable spinning

Nick Piggin
2007-11-02T06:30:41Z

On Thu, Nov 01, 2007 at 06:17:42PM -0700, Linus Torvalds wrote:
>
>
> On Fri, 2 Nov 2007, Nick Piggin wrote:
> >
> > But we do want to allow forced COW faults for MAP_PRIVATE mappings. gdb
> > uses this for inserting breakpoints (but fortunately, a COW page in a
> > MAP_PRIVATE mapping is a much more natural thing for the VM).
>
> Yes, I phrased that badly. I meant that I'd be happier if we got rid of
> VM_MAYSHARE entirely, and just used VM_SHARED. I thought we already made
> them always be the same (and any VM_MAYSHARE use is historical).

Oh yeah, I think it would probably be clearer to use VM_SHARED == MAP_SHARED,
and test the write permission explicitly. Though there could be something
I missed that makes it not as easy as it sounds... probably something best
left for Hugh ;)