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Subject[PATCH 5.10 106/199] can: dev: can_restart: fix use after free bug
Date
From: Vincent Mailhol <mailhol.vincent@wanadoo.fr>

[ Upstream commit 03f16c5075b22c8902d2af739969e878b0879c94 ]

After calling netif_rx_ni(skb), dereferencing skb is unsafe.
Especially, the can_frame cf which aliases skb memory is accessed
after the netif_rx_ni() in:
stats->rx_bytes += cf->len;

Reordering the lines solves the issue.

Fixes: 39549eef3587 ("can: CAN Network device driver and Netlink interface")
Link: https://lore.kernel.org/r/20210120114137.200019-2-mailhol.vincent@wanadoo.fr
Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/can/dev.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
index 81e39d7507d8f..09879aea9f7cc 100644
--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -592,11 +592,11 @@ static void can_restart(struct net_device *dev)

cf->can_id |= CAN_ERR_RESTARTED;

- netif_rx_ni(skb);
-
stats->rx_packets++;
stats->rx_bytes += cf->can_dlc;

+ netif_rx_ni(skb);
+
restart:
netdev_dbg(dev, "restarted\n");
priv->can_stats.restarts++;
--
2.27.0


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