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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, Hangyu Hua <hbh25y@gmail.com>,
        Marc Kleine-Budde <mkl@pengutronix.de>
Subject: [PATCH 5.10 593/599] can: m_can: m_can_tx_handler(): fix use after free of skb
Date:   Tue,  5 Apr 2022 09:34:47 +0200
Message-Id: <20220405070316.487398000@linuxfoundation.org>
In-Reply-To: <20220405070258.802373272@linuxfoundation.org>
References: <20220405070258.802373272@linuxfoundation.org>
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From: Marc Kleine-Budde <mkl@pengutronix.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@vger.kernel.org
Reported-by: Hangyu Hua <hbh25y@gmail.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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
@@ -1491,8 +1491,6 @@ static netdev_tx_t m_can_tx_handler(stru
 					 M_CAN_FIFO_DATA(i / 4),
 					 *(u32 *)(cf->data + i));
 
-		can_put_echo_skb(skb, dev, 0);
-
 		if (cdev->can.ctrlmode & CAN_CTRLMODE_FD) {
 			cccr = m_can_read(cdev, M_CAN_CCCR);
 			cccr &= ~(CCCR_CMR_MASK << CCCR_CMR_SHIFT);
@@ -1509,6 +1507,9 @@ static netdev_tx_t m_can_tx_handler(stru
 			m_can_write(cdev, M_CAN_CCCR, cccr);
 		}
 		m_can_write(cdev, M_CAN_TXBTIE, 0x1);
+
+		can_put_echo_skb(skb, dev, 0);
+
 		m_can_write(cdev, M_CAN_TXBAR, 0x1);
 		/* End of xmit function for version 3.0.x */
 	} else {