linux-kernel - [PATCH 4.19 48/48] can: m_can: m_can_tx_handler(): fix use after free of skb

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Message-Id: <20220719114524.075476331@linuxfoundation.org>
Date:   Tue, 19 Jul 2022 13:54:25 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hangyu Hua <hbh25y@...il.com>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>
Subject: [PATCH 4.19 48/48] can: m_can: m_can_tx_handler(): fix use after free of skb

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

commit 2e8e79c416aae1de224c0f1860f2e3350fa171f8 upstream.

can_put_echo_skb() will clone skb then free the skb. Move the
can_put_echo_skb() for the m_can version 3.0.x directly before the
start of the xmit in hardware, similar to the 3.1.x branch.

Fixes: 80646733f11c ("can: m_can: update to support CAN FD features")
Link: https://lore.kernel.org/all/20220317081305.739554-1-mkl@pengutronix.de
Cc: stable@...r.kernel.org
Reported-by: Hangyu Hua <hbh25y@...il.com>
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
[sudip: adjust context]
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@...il.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/can/m_can/m_can.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -1438,8 +1438,6 @@ static netdev_tx_t m_can_start_xmit(stru
 					 M_CAN_FIFO_DATA(i / 4),
 					 *(u32 *)(cf->data + i));
 
-		can_put_echo_skb(skb, dev, 0);
-
 		if (priv->can.ctrlmode & CAN_CTRLMODE_FD) {
 			cccr = m_can_read(priv, M_CAN_CCCR);
 			cccr &= ~(CCCR_CMR_MASK << CCCR_CMR_SHIFT);
@@ -1456,6 +1454,9 @@ static netdev_tx_t m_can_start_xmit(stru
 			m_can_write(priv, M_CAN_CCCR, cccr);
 		}
 		m_can_write(priv, M_CAN_TXBTIE, 0x1);
+
+		can_put_echo_skb(skb, dev, 0);
+
 		m_can_write(priv, M_CAN_TXBAR, 0x1);
 		/* End of xmit function for version 3.0.x */
 	} else {