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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Marc Kleine-Budde <mkl@pengutronix.de>
Subject: [PATCH 4.9 22/92] can: dev: __can_get_echo_skb(): Dont crash the kernel if can_priv::echo_skb is accessed out of bounds
Date:   Thu, 29 Nov 2018 15:11:51 +0100
Message-Id: <20181129140108.138246702@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Marc Kleine-Budde <mkl@pengutronix.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.

Cc: linux-stable <stable@vger.kernel.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 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
@@ -457,7 +457,11 @@ 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