On Tue, 2024-04-09 at 17:41 -0700, Kui-Feng Lee wrote:
[...]
> Any access to elements other than the first one would be rejected.
I'm not sure this is true, could you please point me to a specific
check in the code that enforces access to go to the first element?
The check added in this patch only enforces correct alignment with
array element start.
Other than this, the patch looks good to me.
[...]
> @@ -5448,7 +5448,10 @@ static int check_map_access(struct bpf_verifier_env *env, u32 regno,
> verbose(env, "kptr access cannot have variable offset\n");
> return -EACCES;
> }
> - if (p != off + reg->var_off.value) {
> + var_p = off + reg->var_off.value;
> + elem_size = field->size / field->nelems;
> + if (var_p < p || var_p >= p + field->size ||
> + (var_p - p) % elem_size) {
> verbose(env, "kptr access misaligned expected=%u off=%llu\n",
> p, off + reg->var_off.value);
> return -EACCES;
