On 2024-09-12 05:06:36 [-0700], Breno Leitao wrote: > Hello Sebastian, Jakub, Hi, > I've seen some crashes in 6.11-rc7 that seems related to 401cb7dae8130 > ("net: Reference bpf_redirect_info via task_struct on PREEMPT_RT."). > > Basically bpf_net_context is NULL, and it is being dereferenced by > bpf_net_ctx->ri.kern_flags (offset 0x38) in the following code. > > static inline struct bpf_redirect_info *bpf_net_ctx_get_ri(void) > { > struct bpf_net_context *bpf_net_ctx = bpf_net_ctx_get(); > if (!(bpf_net_ctx->ri.kern_flags & BPF_RI_F_RI_INIT)) { > > That said, it means that bpf_net_ctx_get() is returning NULL. > > This stack is coming from the bpf function bpf_redirect() > BPF_CALL_2(bpf_redirect, u32, ifindex, u64, flags) > { > struct bpf_redirect_info *ri = bpf_net_ctx_get_ri(); > > > Since I don't think there is XDP involved, I wondering if we need some > preotection before calling bpf_redirect() This origins in netkit_xmit(). If my memory serves me, then Daniel told me that netkit is not doing any redirect and therefore does not need "this". This must have been during one of the first "designs"/ versions. If you are saying, that this is possible then something must be done. Either assign a context or reject the bpf program. Sebastian