netdev - [PATCH net-next] macsec: don't free NULL metadata

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Message-Id: <60f2a1965fe553e2cade9472407d0fafff8de8ce.1663923580.git.sd@queasysnail.net>
Date:   Fri, 23 Sep 2022 11:07:09 +0200
From:   Sabrina Dubroca <sd@...asysnail.net>
To:     netdev@...r.kernel.org
Cc:     Lior Nahmanson <liorna@...dia.com>, Raed Salem <raeds@...dia.com>,
        Saeed Mahameed <saeedm@...dia.com>,
        Sabrina Dubroca <sd@...asysnail.net>
Subject: [PATCH net-next] macsec: don't free NULL metadata_dst

Commit 0a28bfd4971f added a metadata_dst to each tx_sc, but that's
only allocated when macsec_add_dev has run, which happens after device
registration. If the requested or computed SCI already exists, or if
linking to the lower device fails, we will panic because
metadata_dst_free can't handle NULL.

Reproducer:
    ip link add link $lower type macsec
    ip link add link $lower type macsec

Fixes: 0a28bfd4971f ("net/macsec: Add MACsec skb_metadata_dst Tx Data path support")
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 617f850bdb3a..ebcfe87bed23 100644
--- a/drivers/net/macsec.c
+++ b/drivers/net/macsec.c
@@ -3734,7 +3734,8 @@ static void macsec_free_netdev(struct net_device *dev)
 {
 	struct macsec_dev *macsec = macsec_priv(dev);
 
-	metadata_dst_free(macsec->secy.tx_sc.md_dst);
+	if (macsec->secy.tx_sc.md_dst)
+		metadata_dst_free(macsec->secy.tx_sc.md_dst);
 	free_percpu(macsec->stats);
 	free_percpu(macsec->secy.tx_sc.stats);
 
-- 
2.37.3