Re: [PATCH bpf 1/2] uprobes/x86: Fix red zone clobbering in nop5 optimization

[Oleg Nesterov <oleg@redhat.com>]

On 05/11, Andrii Nakryiko wrote:
>
> On Mon, May 11, 2026 at 7:45 AM Oleg Nesterov <oleg@redhat.com> wrote:
> >
> > On 05/08, Andrii Nakryiko wrote:
> > >
> > > +static bool resolve_uprobe_addr(unsigned long ip, unsigned long *probe_addr)
> > >  {
> > > -     struct vm_area_struct *vma = vma_lookup(current->mm, ip);
> > > +     struct uprobes_state *state = &current->mm->uprobes_state;
> >
> > it seems that there is a problem, with or without this change...
> >
> > Lets forget about this patch for the moment, I am still trying to understand it.
> >
> > What if register_for_each_vma() calls install_breakpoint(vma) and
> > vma->mm != current->mm ?
> >
> > In this case install_breakpoint() path will call __is_optimized() and then
> > __in_uprobe_trampoline() which does vma_lookup(current->mm). This looks
> > obviously wrong ?
> >
> > And unless I am totally confused, this patch "inherits" the problem...
> >
> > No?
> >
>
> Yes, sashiko called this out as well. I'm going to pass mm explicitly
> into is_optimized and all the way to resolve_uprobe_addr(), easy fix.

Aah... found it: https://sashiko.dev/#/patchset/20260509003146.976844-1-andrii%40kernel.org

And note that sashiko is more clever than me; I didn't realize that _unregister()
has more problems with current->mm :/

> But we should have a stand-alone easily backportable fix for this even
> without my changes, yes. I can add it as pre-patch or send separately.

Agreed. This deserves another/simple fix. If nothing else, for documentation.

Oleg.