netdev - [Patch net] cls_flower: call nla_ok() before nla

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Message-Id: <20210112025548.19107-1-xiyou.wangcong@gmail.com>
Date:   Mon, 11 Jan 2021 18:55:48 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     netdev@...r.kernel.org
Cc:     Cong Wang <cong.wang@...edance.com>,
        syzbot+2624e3778b18fc497c92@...kaller.appspotmail.com,
        Pieter Jansen van Vuuren 
        <pieter.jansenvanvuuren@...ronome.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Xin Long <lucien.xin@...il.com>, Jiri Pirko <jiri@...nulli.us>
Subject: [Patch net] cls_flower: call nla_ok() before nla_next()

From: Cong Wang <cong.wang@...edance.com>

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@...kaller.appspotmail.com
Fixes: 0a6e77784f49 ("net/sched: allow flower to match tunnel options")
Fixes: 79b1011cb33d ("net: sched: allow flower to match erspan options")
Cc: Pieter Jansen van Vuuren <pieter.jansenvanvuuren@...ronome.com>
Cc: Jamal Hadi Salim <jhs@...atatu.com>
Cc: Xin Long <lucien.xin@...il.com>
Cc: Jiri Pirko <jiri@...nulli.us>
Signed-off-by: Cong Wang <cong.wang@...edance.com>
---
 net/sched/cls_flower.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
index 1319986693fc..e265c443536e 100644
--- a/net/sched/cls_flower.c
+++ b/net/sched/cls_flower.c
@@ -1272,6 +1272,8 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
 
 		nla_opt_msk = nla_data(tb[TCA_FLOWER_KEY_ENC_OPTS_MASK]);
 		msk_depth = nla_len(tb[TCA_FLOWER_KEY_ENC_OPTS_MASK]);
+		if (!nla_ok(nla_opt_msk, msk_depth))
+			return -EINVAL;
 	}
 
 	nla_for_each_attr(nla_opt_key, nla_enc_key,
@@ -1308,7 +1310,7 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
 				return -EINVAL;
 			}
 
-			if (msk_depth)
+			if (nla_ok(nla_opt_msk, msk_depth))
 				nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
 			break;
 		case TCA_FLOWER_KEY_ENC_OPTS_VXLAN:
@@ -1341,7 +1343,7 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
 				return -EINVAL;
 			}
 
-			if (msk_depth)
+			if (nla_ok(nla_opt_msk, msk_depth))
 				nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
 			break;
 		case TCA_FLOWER_KEY_ENC_OPTS_ERSPAN:
@@ -1374,7 +1376,7 @@ static int fl_set_enc_opt(struct nlattr **tb, struct fl_flow_key *key,
 				return -EINVAL;
 			}
 
-			if (msk_depth)
+			if (nla_ok(nla_opt_msk, msk_depth))
 				nla_opt_msk = nla_next(nla_opt_msk, &msk_depth);
 			break;
 		default:
-- 
2.25.1