Re: [PATCH bpf-next] bpf: Fix suspicious RCU usage for sleepable bpf_get_stack()

[Feng Yang]

On Wed, 28 Oct 2026 20:51:47 +0800, Songsen Yang wrote:
> Hi Feng,
> 
> I hit the same root cause independently via syzbot and sent a fix a
> few hours after yours, without having seen this patch -- sorry for the
> overlap:
>
>  https://lore.kernel.org/bpf/20261028121859.994-1-yangsong...@insta360.com/

Hi Songsen,

Please don't worry about the overlap.

I hadn't noticed the issue Sashiko raised when I prepared my fix; 
It looks like a pt_regs on the stack can fix this.:

        BPF_CALL_4(bpf_get_stack_raw_tp_sleepable, struct 
bpf_raw_tracepoint_args *, args,
                   void *, buf, u32, size, u64, flags)
        {
                struct pt_regs regs;

                perf_fetch_caller_regs(&regs);
                return bpf_get_stack_sleepable((unsigned long) &regs, (unsigned 
long) buf,
                                               (unsigned long) size, flags, 0);
        }

That said, I think your approach is the simpler one and the better fit
for the fix itself.  So if the maintainers prefer your version, feel
free to ignore my patch.

Thanks,
Feng