Re: [Patch net v2] cls_flower: call nla_ok() before nla_next()
From: Jakub Kicinski <kuba@kernel.org>
Date: 2021-01-14 18:39:35
On Thu, 14 Jan 2021 08:38:22 -0800 Cong Wang wrote:
From: Cong Wang <redacted>
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: syzbot+2624e3778b18fc497c92@syzkaller.appspotmail.com
Fixes: 0a6e77784f49 ("net/sched: allow flower to match tunnel options")
Fixes: 79b1011cb33d ("net: sched: allow flower to match erspan options")quoted hunk ↗ jump to hunk
@@ -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;