linux-kernel - [PATCH 3.16 177/305] can: dev: __can_get_echo_skb(): Don't crash the kernel if can_priv::echo

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Message-ID: <lsq.1549201508.324989971@decadent.org.uk>
Date:   Sun, 03 Feb 2019 14:45:08 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Marc Kleine-Budde" <mkl@...gutronix.de>
Subject: [PATCH 3.16 177/305] can: dev: __can_get_echo_skb(): Don't crash
 the kernel if can_priv::echo_skb is accessed out of bounds

3.16.63-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Marc Kleine-Budde <mkl@...gutronix.de>

commit e7a6994d043a1e31d5b17706a22ce33d2a3e4cdc upstream.

If the "struct can_priv::echo_skb" is accessed out of bounds would lead
to a kernel crash. Better print a sensible warning message instead and
try to recover.

Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/net/can/dev.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/net/can/dev.c
+++ b/drivers/net/can/dev.c
@@ -426,7 +426,11 @@ struct sk_buff *__can_get_echo_skb(struc
 {
 	struct can_priv *priv = netdev_priv(dev);
 
-	BUG_ON(idx >= priv->echo_skb_max);
+	if (idx >= priv->echo_skb_max) {
+		netdev_err(dev, "%s: BUG! Trying to access can_priv::echo_skb out of bounds (%u/max %u)\n",
+			   __func__, idx, priv->echo_skb_max);
+		return NULL;
+	}
 
 	if (priv->echo_skb[idx]) {
 		/* Using "struct canfd_frame::len" for the frame