[PATCH 5.10 31/65] macsec: fix NULL deref in macsec_add_rxsa

[Greg Kroah-Hartman]

From: Sabrina Dubroca <sd@xxxxxxxxxxxxxxx>

[ Upstream commit f46040eeaf2e523a4096199fd93a11e794818009 ]

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@xxxxxxxxxx>
Signed-off-by: Sabrina Dubroca <sd@xxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 789a124809e3..0b53c7cadd87 100644
--- a/drivers/net/macsec.c
+++ b/drivers/net/macsec.c
@@ -1750,7 +1750,8 @@ 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();
-- 
2.35.1