Re: [PATCH v1 0/7] Remove in-tree usage of MAP_DENYWRITE

[Al Viro]

On Sat, Aug 14, 2021 at 01:57:31AM +0000, Al Viro wrote:
> On Fri, Aug 13, 2021 at 02:58:57PM -1000, Linus Torvalds wrote:
> > On Fri, Aug 13, 2021 at 2:54 PM Linus Torvalds
> > <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> > >
> > > And nobody really complained when we weakened it, so maybe removing it
> > > entirely might be acceptable.
> > 
> > I guess we could just try it and see... Worst comes to worst, we'll
> > have to put it back, but at least we'd know what crazy thing still
> > wants it..
> 
> Umm...  I'll need to go back and look through the thread, but I'm
> fairly sure that there used to be suckers that did replacement of
> binary that way (try to write, count on exclusion with execve while
> it's being written to) instead of using rename.  Install scripts
> of weird crap and stuff like that...

... and before anyone goes off - I certainly agree that using that
behaviour is not a good idea and had never been one.  All I'm saying
is that there at least used to be very random (and rarely exercised)
bits of userland relying upon that behaviour.