netdev - [PATCH net 1/4] macsec: fix NULL deref in macsec_add

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Message-Id: <7b3fd03e1a46047e5ffe2a389fe74501f0a93206.1656519221.git.sd@queasysnail.net>
Date:   Fri, 22 Jul 2022 11:16:27 +0200
From:   Sabrina Dubroca <sd@...asysnail.net>
To:     netdev@...r.kernel.org
Cc:     Era Mayflower <mayflowerera@...il.com>,
        Sabrina Dubroca <sd@...asysnail.net>,
        Frantisek Sumsal <fsumsal@...hat.com>
Subject: [PATCH net 1/4] macsec: fix NULL deref in macsec_add_rxsa

Commit 48ef50fa866a added a test on tb_sa[MACSEC_SA_ATTR_PN], but
nothing guarantees that it's not NULL at this point. The same code was
added to macsec_add_txsa, but there it's not a problem because
validate_add_txsa checks that the MACSEC_SA_ATTR_PN attribute is
present.

Note: it's not possible to reproduce with iproute, because iproute
doesn't allow creating an SA without specifying the PN.

Fixes: 48ef50fa866a ("macsec: Netlink support of XPN cipher suites (IEEE 802.1AEbw)")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=208315
Reported-by: Frantisek Sumsal <fsumsal@...hat.com>
Signed-off-by: Sabrina Dubroca <sd@...asysnail.net>
---
 drivers/net/macsec.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c
index 817577e713d7..769a1eca6bd8 100644
--- a/drivers/net/macsec.c
+++ b/drivers/net/macsec.c
@@ -1753,7 +1753,8 @@ static int macsec_add_rxsa(struct sk_buff *skb, struct genl_info *info)
 	}
 
 	pn_len = secy->xpn ? MACSEC_XPN_PN_LEN : MACSEC_DEFAULT_PN_LEN;
-	if (nla_len(tb_sa[MACSEC_SA_ATTR_PN]) != pn_len) {
+	if (tb_sa[MACSEC_SA_ATTR_PN] &&
+	    nla_len(tb_sa[MACSEC_SA_ATTR_PN]) != pn_len) {
 		pr_notice("macsec: nl: add_rxsa: bad pn length: %d != %d\n",
 			  nla_len(tb_sa[MACSEC_SA_ATTR_PN]), pn_len);
 		rtnl_unlock();
-- 
2.36.1