On Thu, 14 Jan 2021 08:38:22 -0800 Cong Wang wrote:
> From: Cong Wang <[email protected]>
>
> fl_set_enc_opt() simply checks if there are still bytes left to parse,
> but this is not sufficent as syzbot seems to be able to generate
> malformatted netlink messages. nla_ok() is more strict so should be
> used to validate the next nlattr here.
>
> And nla_validate_nested_deprecated() has less strict check too, it is
> probably too late to switch to the strict version, but we can just
> call nla_ok() too after it.
>
> Reported-and-tested-by: [email protected]
> Fixes: 0a6e77784f49 ("net/sched: allow flower to match tunnel options")
> Fixes: 79b1011cb33d ("net: sched: allow flower to match erspan options")
> @@ -1340,9 +1341,6 @@ static int fl_set_enc_opt(struct nlattr **tb, struct
> fl_flow_key *key,
> NL_SET_ERR_MSG(extack, "Key and mask miss
> aligned");
> return -EINVAL;
> }
> -
> - if (msk_depth)
> - nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
> break;
> case TCA_FLOWER_KEY_ENC_OPTS_ERSPAN:
> if (key->enc_opts.dst_opt_type) {
> @@ -1373,14 +1371,17 @@ static int fl_set_enc_opt(struct nlattr **tb, struct
> fl_flow_key *key,
> NL_SET_ERR_MSG(extack, "Key and mask miss
> aligned");
> return -EINVAL;
> }
> -
> - if (msk_depth)
> - nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
> break;
> default:
> NL_SET_ERR_MSG(extack, "Unknown tunnel option type");
> return -EINVAL;
> }
> +
> + if (!nla_ok(nla_opt_msk, msk_depth)) {
> + NL_SET_ERR_MSG(extack, "Mask attribute is invalid");
> + return -EINVAL;
> + }
> + nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
we lost the if (msk_depth) now, nla_opt_msk may be NULL -
neither nla_ok() nor nla_next() take NULL
> }
>
> return 0;
