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net: mctp: fix device leak on probe failure

PATCH Applied Johan Hovold 3 participants 4 messages Mar 5 – Mar 7

Subsystems (4)
Networking Network drivers Stable branch Management component transport protocol (MCTP)
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Johan Hovold

author
#0 lore raw

PATCH 1/1 net: mctp: fix device leak on probe failure

Driver core holds a reference to the USB interface and its parent USB device while the interface is bound to a driver and there is no need to take additional references unless the structures are needed after disconnect.

This driver takes a reference to the USB device during probe but does not to release it on probe failures.

Drop the redundant device reference to fix the leak, reduce cargo culting, make it easier to spot drivers where an extra reference is needed, and reduce the risk of further memory leaks.

Fixes 0791c0327a6e ("net: mctp: Add MCTP USB transport driver")
Cc [email protected] # 6.15
Cc Jeremy Kerr <[email protected]>
Signed-off-by Johan Hovold <[email protected]>
---
 drivers/net/mctp/mctp-usb.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)
drivers/net/mctp/mctp-usb.c +1 -2
index ef860cfc629f..3b5dff144177 100644
@@ -329,7 +329,7 @@ static int mctp_usb_probe(struct usb_interface *intf,
 	SET_NETDEV_DEV(netdev, &intf->dev);
 	dev = netdev_priv(netdev);
 	dev->netdev = netdev;
-	dev->usbdev = usb_get_dev(interface_to_usbdev(intf));
+	dev->usbdev = interface_to_usbdev(intf);
 	dev->intf = intf;
 	usb_set_intfdata(intf, dev);
 

@@ -365,7 +365,6 @@ static void mctp_usb_disconnect(struct usb_interface *intf)
 	mctp_unregister_netdev(dev->netdev);
 	usb_free_urb(dev->tx_urb);
 	usb_free_urb(dev->rx_urb);
-	usb_put_dev(dev->usbdev);
 	free_netdev(dev->netdev);
 }
Signature · 1 line
2.52.0
maintainer Acked-by on v1 1/1
#1 lore raw

Hi John,

Quoted 11 lines

Driver core holds a reference to the USB interface and its parent USB device while the interface is bound to a driver and there is no need to take additional references unless the structures are needed after disconnect.

This driver takes a reference to the USB device during probe but does not to release it on probe failures.

Drop the redundant device reference to fix the leak, reduce cargo culting, make it easier to spot drivers where an extra reference is needed, and reduce the risk of further memory leaks.

Sounds good, but I would suggest syncing with Greg K-H too; he's in the process of doing a v2 for the same thing:

https://lore.kernel.org/netdev/2026022539-punch-supper-884c@gregkh/

Given the discussion there, this looks in-line with the longer-term move from usb_get_dev(), so:

Acked-by Jeremy Kerr <[email protected]>

Thanks,

Jeremy

maintainer
#2 lore raw

+CC Greg

Context is Johan's patch at
https://lore.kernel.org/netdev/[email protected]/

Cheers,

Jeremy

Quoted 28 lines

Hi John,

Quoted 11 lines

Driver core holds a reference to the USB interface and its parent USB device while the interface is bound to a driver and there is no need to take additional references unless the structures are needed after disconnect.

This driver takes a reference to the USB device during probe but does not to release it on probe failures.

Drop the redundant device reference to fix the leak, reduce cargo culting, make it easier to spot drivers where an extra reference is needed, and reduce the risk of further memory leaks.

Sounds good, but I would suggest syncing with Greg K-H too; he's in the process of doing a v2 for the same thing:

  https://lore.kernel.org/netdev/2026022539-punch-supper-884c@gregkh/

Given the discussion there, this looks in-line with the longer-term move from usb_get_dev(), so:

Acked-by Jeremy Kerr <[email protected]>

Thanks,

Jeremy

CI Applied
#3 lore raw
In reply to Johan Hovold
This patch was applied to netdev/net.git (main) by Jakub Kicinski <[email protected]>:

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <[email protected]>:

Quoted 9 lines · On Thu, 5 Mar 2026 11:45:49 +0100 you wrote:

Driver core holds a reference to the USB interface and its parent USB device while the interface is bound to a driver and there is no need to take additional references unless the structures are needed after disconnect.

This driver takes a reference to the USB device during probe but does not to release it on probe failures.

[...]

Here is the summary with links:
- net: mctp: fix device leak on probe failure

    https://git.kernel.org/netdev/net/c/224a0d284c3c

You are awesome, thank you!

Signature · 2 lines
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