On Thu, May 21, 2020 at 6:07 PM Alexei Starovoitov
<alexei.starovoitov@xxxxxxxxx> wrote:
>
> On Sun, May 17, 2020 at 12:57:21PM -0700, Andrii Nakryiko wrote:
> > - if (off < 0 || size < 0 || (size == 0 && !zero_size_allowed) ||
> > - off + size > map->value_size) {
> > - verbose(env, "invalid access to map value, value_size=%d off=%d size=%d\n",
> > - map->value_size, off, size);
> > - return -EACCES;
> > - }
> > - return 0;
> > + if (off >= 0 && size_ok && off + size <= mem_size)
> > + return 0;
> > +
> > + verbose(env, "invalid access to memory, mem_size=%u off=%d size=%d\n",
> > + mem_size, off, size);
> > + return -EACCES;
>
> iirc invalid access to map value is one of most common verifier errors that
> people see when they're use unbounded access. Generalizing it to memory is
> technically correct, but it makes the message harder to decipher.
> What is 'mem_size' ? Without context it is difficult to guess that
> it's actually size of map value element.
> Could you make this error message more human friendly depending on
> type of pointer?
yep, sure, better verifier errors are extremely important, I think
>
> > if (err) {
> > - verbose(env, "R%d min value is outside of the array range\n",
> > + verbose(env, "R%d min value is outside of the memory region\n",
> > regno);
> > return err;
> > }
> > @@ -2518,18 +2527,38 @@ static int check_map_access(struct bpf_verifier_env *env, u32 regno,
> > * If reg->umax_value + off could overflow, treat that as unbounded too.
> > */
> > if (reg->umax_value >= BPF_MAX_VAR_OFF) {
> > - verbose(env, "R%d unbounded memory access, make sure to bounds check any array access into a map\n",
> > + verbose(env, "R%d unbounded memory access, make sure to bounds check any memory region access\n",
> > regno);
> > return -EACCES;
> > }
> > - err = __check_map_access(env, regno, reg->umax_value + off, size,
> > + err = __check_mem_access(env, reg->umax_value + off, size, mem_size,
> > zero_size_allowed);
> > - if (err)
> > - verbose(env, "R%d max value is outside of the array range\n",
> > + if (err) {
> > + verbose(env, "R%d max value is outside of the memory region\n",
> > regno);
>
> I'm not that worried about above three generalizations of errors,
> but if you can make it friendly by describing type of memory region
> I think it will be a plus.
I agree, will update
