Re: [PATCH bpf 1/2] mm: Fix copy_from_user_nofault().

[Salvatore Bonaccorso <carnil@debian.org>]

Hi,

On Sat, Mar 25, 2023 at 12:47:17PM -0700, Alexei Starovoitov wrote:
> On Sat, Mar 25, 2023 at 7:55 AM Florian Lehner <dev@der-flo.net> wrote:
> >
> > With this patch applied on top of bpf/bpf-next (55fbae05) the system no longer runs into a total freeze as reported in https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1033398.
> >
> > Tested-by: Florian Lehner <dev@der-flo.net>
> 
> Thanks for testing and for bumping the thread.
> The fix slipped through the cracks.
> 
> Looking at the stack trace in bugzilla the patch set
> should indeed fix the issue, since the kernel is deadlocking on:
> copy_from_user_nofault -> check_object_size -> find_vmap_area -> spin_lock
> 
> I'm travelling this and next week, so if you can take over
> the whole patch set and roll in the tweak that was proposed back in January:
> 
> -       if (is_vmalloc_addr(ptr)) {
> +       if (is_vmalloc_addr(ptr) && !pagefault_disabled())
> 
> and respin for the bpf tree our group maintainers can review and apply
> while I'm travelling.

Anyone can pick it up as suggested by Alexei, and propose that to the
bpf tree maintainers?

Regards,
Salvatore