On Tue, Aug 19, 2025 at 4:24 PM Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote:
>
> On 8/15/25 10:29 AM, Haoran Jiang wrote:
> > In some eBPF programs, the return value is a pointer.
> > When the kernel call an eBPF program (such as struct_ops),
> > it expects a 64-bit address to be returned, but instead a 32-bit value.
> >
> > Before applying this patch:
> > ./test_progs -a ns_bpf_qdisc
> > CPU 7 Unable to handle kernel paging request at virtual
> > address 0000000010440158.
> >
> > As shown in the following test case,
> > bpf_fifo_dequeue return value is a pointer.
> > progs/bpf_qdisc_fifo.c
> >
> > SEC("struct_ops/bpf_fifo_dequeue")
> > struct sk_buff *BPF_PROG(bpf_fifo_dequeue, struct Qdisc *sch)
> > {
> > struct sk_buff *skb = NULL;
> > ........
> > skb = bpf_kptr_xchg(&skbn->skb, skb);
> > ........
> > return skb;
> > }
> >
> > kernel call bpf_fifo_dequeue：
> > net/sched/sch_generic.c
> >
> > static struct sk_buff *dequeue_skb(struct Qdisc *q, bool *validate,
> > int *packets)
> > {
> > struct sk_buff *skb = NULL;
> > ........
> > skb = q->dequeue(q);
> > .........
> > }
> > When accessing the skb, an address exception error will occur.
> > because the value returned by q->dequeue at this point is a 32-bit
> > address rather than a 64-bit address.
> >
> > After applying the patch：
> > ./test_progs -a ns_bpf_qdisc
> > Warning: sch_htb: quantum of class 10001 is small. Consider r2q change.
> > 213/1 ns_bpf_qdisc/fifo:OK
> > 213/2 ns_bpf_qdisc/fq:OK
> > 213/3 ns_bpf_qdisc/attach to mq:OK
> > 213/4 ns_bpf_qdisc/attach to non root:OK
> > 213/5 ns_bpf_qdisc/incompl_ops:OK
> > 213 ns_bpf_qdisc:OK
> > Summary: 1/5 PASSED, 0 SKIPPED, 0 FAILED
> >
> > Fixes: 73c359d1d356 ("LoongArch: BPF: Sign-extend return values")
> > Signed-off-by: Jinyang He <hejinyang@xxxxxxxxxxx>
> > Signed-off-by: Haoran Jiang <jianghaoran@xxxxxxxxxx>
>
> Huacai, are you routing the fix or want us to route via bpf tree?
I will take it, but I'm waiting Tiezhu's Ack now.
Huacai
>
> Thanks,
> Daniel
