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From:   Pavel Skripkin <paskripkin@gmail.com>
To:     mkl@pengutronix.de, yasushi.shoji@gmail.com, wg@grandegger.com
Cc:     linux-can@vger.kernel.org, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org, Pavel Skripkin <paskripkin@gmail.com>
Subject: [PATCH] net: can: add missing urb->transfer_dma initialization
Date:   Sun, 25 Jul 2021 13:36:30 +0300
Message-Id: <20210725103630.23864-1-paskripkin@gmail.com>
In-Reply-To: <20210725094246.pkdpvl5aaaftur3a@pengutronix.de>
References: <20210725094246.pkdpvl5aaaftur3a@pengutronix.de>
MIME-Version: 1.0
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Precedence: bulk

Yasushi reported, that his Microchip CAN Analyzer stopped working since
commit 91c02557174b ("can: mcba_usb: fix memory leak in mcba_usb").
The problem was in missing urb->transfer_dma initialization.

In my previous patch to this driver I refactored mcba_usb_start() code to
avoid leaking usb coherent buffers. To achive it, I passed local stack
variable to usb_alloc_coherent() and then saved it to private array to
correctly free all coherent buffers on ->close() call. But I forgot to
inialize urb->transfer_dma with variable passed to usb_alloc_coherent().

All of this was causing device to not work, since dma addr 0 is not valid
and following log can be found on bug report page, which points exactly to
problem described above.

[   33.862175] DMAR: [DMA Write] Request device [00:14.0] PASID ffffffff fault addr 0 [fault reason 05] PTE Write access is not set

Bug report: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=990850

Reported-by: Yasushi SHOJI <yasushi.shoji@gmail.com>
Fixes: 91c02557174b ("can: mcba_usb: fix memory leak in mcba_usb")
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
---
 drivers/net/can/usb/mcba_usb.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/can/usb/mcba_usb.c b/drivers/net/can/usb/mcba_usb.c
index a45865bd7254..a1a154c08b7f 100644
--- a/drivers/net/can/usb/mcba_usb.c
+++ b/drivers/net/can/usb/mcba_usb.c
@@ -653,6 +653,8 @@ static int mcba_usb_start(struct mcba_priv *priv)
 			break;
 		}
 
+		urb->transfer_dma = buf_dma;
+
 		usb_fill_bulk_urb(urb, priv->udev,
 				  usb_rcvbulkpipe(priv->udev, MCBA_USB_EP_IN),
 				  buf, MCBA_USB_RX_BUFF_SIZE,
-- 
2.32.0