linux-kernel - [PATCH 4.19 30/74] can: pch_can: pch_can_rx

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Message-Id: <20211213092931.817161270@linuxfoundation.org>
Date:   Mon, 13 Dec 2021 10:30:01 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Vincent Mailhol <mailhol.vincent@...adoo.fr>,
        Marc Kleine-Budde <mkl@...gutronix.de>
Subject: [PATCH 4.19 30/74] can: pch_can: pch_can_rx_normal: fix use after free

From: Vincent Mailhol <mailhol.vincent@...adoo.fr>

commit 94cddf1e9227a171b27292509d59691819c458db upstream.

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.")
Link: https://lore.kernel.org/all/20211123111654.621610-1-mailhol.vincent@wanadoo.fr
Cc: stable@...r.kernel.org
Signed-off-by: Vincent Mailhol <mailhol.vincent@...adoo.fr>
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/net/can/pch_can.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/net/can/pch_can.c
+++ b/drivers/net/can/pch_can.c
@@ -703,11 +703,11 @@ static int pch_can_rx_normal(struct net_
 			cf->data[i + 1] = data_reg >> 8;
 		}
 
-		netif_receive_skb(skb);
 		rcv_pkts++;
 		stats->rx_packets++;
 		quota--;
 		stats->rx_bytes += cf->can_dlc;
+		netif_receive_skb(skb);
 
 		pch_fifo_thresh(priv, obj_num);
 		obj_num++;