Re: [RFC PATCH v2 1/2] mm/mremap: Fix uprobe anon page be overwritten when expanding vma during mremap

[Oleg Nesterov <oleg@redhat.com>]

On 05/27, Lorenzo Stoakes wrote:
>
> On Tue, May 27, 2025 at 05:30:08PM +0200, Oleg Nesterov wrote:
> >
> > >     struct perf_event_attr attr = {
> > >         .type = 9,
> >
> > Cough ;) Yes I too used perf_event_attr.type == 9 when I wrote another
> > test-case. Because I am lazy and this is what I see in
> > /sys/bus/event_source/devices/uprobe/type on my machine.
> >
> > But me should not assume that perf_pmu_register(&perf_uprobe) -> idr_alloc()
> > will return 9.
>
> While I agree we should probably try to do this nicely, in defence of Pu I think
> this is adapted from the syzkaller horror show :P and that code does tend to
> just insert random integers etc.

Not really ;)

syzkaller's reproducer reads /sys/bus/event_source/devices/uprobe/type, see
https://lore.kernel.org/all/20250521092503.3116340-1-pulehui@huaweicloud.com/

In any case. Many thanks to Lehui who investigated this problem!

Oleg.