On Fri, 2023-12-08 at 09:19 -0800, Yonghong Song wrote:
> On 12/8/23 6:34 AM, Eduard Zingerman wrote:
> > On Thu, 2023-12-07 at 18:28 -0800, Yonghong Song wrote:
> > [...]
> > > All context types are defined in include/linux/bpf_types.h.
> > > The context type bpf_nf_ctx is missing.
[...]
> The error message should happen here:
>
> check_mem_access
> ...
> } else if (reg->type == PTR_TO_CTX) {
> check_ptr_off_reg
> __check_ptr_off_reg
> if (!fixed_off_ok && reg->off) {
> verbose(env, "dereference of modified %s ptr R%d off=%d disallowed\n",
> reg_type_str(env, reg->type), regno, reg->off);
> return -EACCES;
> }
> ...
>
> So the verification error message will be emitted earlier, before convert_ctx_access.
> Could you double check?
You are correct and I was unaware of this check. A simple test
"r1 += 8; r0 = *(u64 *)(r1 + 0);" does indeed report an error.
I'll make sure that every context type is annotated with
preserve static offset, thank you for pointing this out.
[...]
