[PATCH] net: mctp: fix device leak on probe failure

[PATCH] net: mctp: fix device leak on probe failure

[Johan Hovold]

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: stable@vger.kernel.org	# 6.15
Cc: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/net/mctp/mctp-usb.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/mctp/mctp-usb.c b/drivers/net/mctp/mctp-usb.c
index ef860cfc629f..3b5dff144177 100644
--- a/drivers/net/mctp/mctp-usb.c
+++ b/drivers/net/mctp/mctp-usb.c
@@ -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);
 }
 
-- 
2.52.0

Re: [PATCH] net: mctp: fix device leak on probe failure

[Jeremy Kerr]

Hi John,

> 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 <jk@codeconstruct.com.au>

Thanks,


Jeremy

Re: [PATCH] net: mctp: fix device leak on probe failure

[Jeremy Kerr]

+CC Greg

Context is Johan's patch at
https://lore.kernel.org/netdev/20260305104549.16110-1-johan@kernel.org/

Cheers,


Jeremy

> Hi John,
> 
> > 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 <jk@codeconstruct.com.au>
> 
> Thanks,
> 
> 
> Jeremy

Re: [PATCH] net: mctp: fix device leak on probe failure

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

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!
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