On Wed, 10 Apr 2019 20:50:20 +0100, Jiong Wang wrote: > @@ -2169,6 +2188,12 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn > value_regno); > if (reg_type_may_be_null(reg_type)) > regs[value_regno].id = ++env->id_gen; > + /* A load of ctx field could have different > + * actual load size with the one encoded in the > + * insn. When the dst is PTR, it is for sure not > + * a sub-register. > + */ > + regs[value_regno].subreg_def = DEF_NOT_SUBREG; Can't the rewrite generate a 32bit load? E.g. reading skb->len will be LDX | W, we still gotta clear the top bits in that case, no? I can't find the explanation of this case with a quick scan of the code and cover letter.. > } > regs[value_regno].type = reg_type; > }
