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[PATCH] can: pch_can: pch_can_rx_normal: fix use after free

From: Vincent Mailhol <hidden>
Date: 2021-11-23 11:17:10
Also in: linux-can, lkml
Subsystem: can network drivers, the rest · Maintainers: Marc Kleine-Budde, Vincent Mailhol, Linus Torvalds

After calling netif_receive_skb(skb), dereferencing skb is unsafe.
Especially, the can_frame cf which aliases skb memory is dereferenced
just after the call netif_receive_skb(skb).

Reordering the lines solves the issue.

Fixes: b21d18b51b31 ("can: Topcliff: Add PCH_CAN driver.")
Signed-off-by: Vincent Mailhol <redacted>
---
 drivers/net/can/pch_can.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/can/pch_can.c b/drivers/net/can/pch_can.c
index 92a54a5fd4c5..964c8a09226a 100644
--- a/drivers/net/can/pch_can.c
+++ b/drivers/net/can/pch_can.c
@@ -692,11 +692,11 @@ static int pch_can_rx_normal(struct net_device *ndev, u32 obj_num, int quota)
 			cf->data[i + 1] = data_reg >> 8;
 		}
 
-		netif_receive_skb(skb);
 		rcv_pkts++;
 		stats->rx_packets++;
 		quota--;
 		stats->rx_bytes += cf->len;
+		netif_receive_skb(skb);
 
 		pch_fifo_thresh(priv, obj_num);
 		obj_num++;
-- 
2.32.0
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