[PATCH 4.19 28/58] can: dev: can_restart: fix use after free bug

Greg Kroah-Hartman
2021-01-26T08:35:59Z

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 f88590074569e..953c6fdc75cc4 100644
--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -579,11 +579,11 @@ 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