linux-kernel - [PATCH] net: macsec: fix double free of percpu stats

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Message-Id: <20230613192220.159407-1-pchelkin@ispras.ru>
Date:   Tue, 13 Jun 2023 22:22:20 +0300
From:   Fedor Pchelkin <pchelkin@...ras.ru>
To:     "David S. Miller" <davem@...emloft.net>
Cc:     Fedor Pchelkin <pchelkin@...ras.ru>,
        Sabrina Dubroca <sd@...asysnail.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Raed Salem <raeds@...dia.com>,
        Lior Nahmanson <liorna@...dia.com>,
        Saeed Mahameed <saeedm@...dia.com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Alexey Khoroshilov <khoroshilov@...ras.ru>,
        lvc-project@...uxtesting.org
Subject: [PATCH] net: macsec: fix double free of percpu stats

Inside macsec_add_dev() we free percpu macsec->secy.tx_sc.stats and
macsec->stats on some of the memory allocation failure paths. However, the
net_device is already registered to that moment: in macsec_newlink(), just
before calling macsec_add_dev(). This means that during unregister process
its priv_destructor - macsec_free_netdev() - will be called and will free
the stats again.

Remove freeing percpu stats inside macsec_add_dev() because
macsec_free_netdev() will correctly free the already allocated ones. The
pointers to unallocated stats stay NULL, and free_percpu() treats that
correctly.

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Fixes: 0a28bfd4971f ("net/macsec: Add MACsec skb_metadata_dst Tx Data path support")
Fixes: c09440f7dcb3 ("macsec: introduce IEEE 802.1AE driver")
Signed-off-by: Fedor Pchelkin <pchelkin@...ras.ru>
---
 drivers/net/macsec.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c
index 3427993f94f7..984dfa5d6c11 100644
--- a/drivers/net/macsec.c
+++ b/drivers/net/macsec.c
@@ -3997,17 +3997,15 @@ static int macsec_add_dev(struct net_device *dev, sci_t sci, u8 icv_len)
 		return -ENOMEM;
 
 	secy->tx_sc.stats = netdev_alloc_pcpu_stats(struct pcpu_tx_sc_stats);
-	if (!secy->tx_sc.stats) {
-		free_percpu(macsec->stats);
+	if (!secy->tx_sc.stats)
 		return -ENOMEM;
-	}
 
 	secy->tx_sc.md_dst = metadata_dst_alloc(0, METADATA_MACSEC, GFP_KERNEL);
-	if (!secy->tx_sc.md_dst) {
-		free_percpu(secy->tx_sc.stats);
-		free_percpu(macsec->stats);
+	if (!secy->tx_sc.md_dst)
+		/* macsec and secy percpu stats will be freed when unregistering
+		 * net_device in macsec_free_netdev()
+		 */
 		return -ENOMEM;
-	}
 
 	if (sci == MACSEC_UNDEF_SCI)
 		sci = dev_to_sci(dev, MACSEC_PORT_ES);
-- 
2.34.1