netdev - [PATCH net-next 2/3] net/sched: act_pedit: check static offsets a priori

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Message-Id: <20230309185158.310994-3-pctammela@mojatatu.com>
Date:   Thu,  9 Mar 2023 15:51:57 -0300
From:   Pedro Tammela <pctammela@...atatu.com>
To:     netdev@...r.kernel.org
Cc:     jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, Pedro Tammela <pctammela@...atatu.com>
Subject: [PATCH net-next 2/3] net/sched: act_pedit: check static offsets a priori

Static key offsets should always be on 32 bit boundaries. Validate them on
create/update time for static offsets and move the datapath validation
for runtime offsets only.

iproute2 already errors out if a given offset and data size cannot be packed
to a 32 bit boundary. This change will make sure users which create/update pedit
instances directly via netlink also error out, instead of finding out
when packets are traversing.

Reviewed-by: Jamal Hadi Salim <jhs@...atatu.com>
Signed-off-by: Pedro Tammela <pctammela@...atatu.com>
---
 net/sched/act_pedit.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
index f4ebe06aeaf2..e42cbfc369ff 100644
--- a/net/sched/act_pedit.c
+++ b/net/sched/act_pedit.c
@@ -242,6 +242,12 @@ static int tcf_pedit_init(struct net *net, struct nlattr *nla,
 	for (i = 0; i < nparms->tcfp_nkeys; ++i) {
 		u32 cur = nparms->tcfp_keys[i].off;
 
+		if (cur % 4) {
+			NL_SET_ERR_MSG_MOD(extack, "Pedit offsets must be on 32bit boundaries");
+			ret = -EINVAL;
+			goto put_chain;
+		}
+
 		/* sanitize the shift value for any later use */
 		nparms->tcfp_keys[i].shift = min_t(size_t,
 						   BITS_PER_TYPE(int) - 1,
@@ -400,12 +406,12 @@ TC_INDIRECT_SCOPE int tcf_pedit_act(struct sk_buff *skb,
 					       sizeof(_d), &_d);
 			if (!d)
 				goto bad;
-			offset += (*d & tkey->offmask) >> tkey->shift;
-		}
 
-		if (offset % 4) {
-			pr_info("tc action pedit offset must be on 32 bit boundaries\n");
-			goto bad;
+			offset += (*d & tkey->offmask) >> tkey->shift;
+			if (offset % 4) {
+				pr_info("tc action pedit offset must be on 32 bit boundaries\n");
+				goto bad;
+			}
 		}
 
 		if (!offset_valid(skb, hoffset + offset)) {
-- 
2.34.1