linux-kernel - Re: [PATCH] USB: usbip: fix null-ptr-deref in status_show

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Message-ID: <352b31e8-f8ef-4207-81a7-0aa22c984aeb@gmail.com>
Date: Wed, 22 Jan 2025 11:56:34 +0300
From: Sergey Shtylyov <sergei.shtylyov@...il.com>
To: Qasim Ijaz <qasdev00@...il.com>, valentina.manea.m@...il.com,
 shuah@...nel.org, i@...ithal.me, gregkh@...uxfoundation.org
Cc: linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
 syzbot <syzbot+83976e47ec1ef91e66f1@...kaller.appspotmail.com>
Subject: Re: [PATCH] USB: usbip: fix null-ptr-deref in status_show_vhci()

On 1/21/25 11:36 PM, Qasim Ijaz wrote:

> If usb_add_hcd() fails in vhci_hcd_probe() (i.e., a probe failure),
> the error path calls usb_remove_hcd() and also sets 
> pdev->dev.driver_data to NULL.
> 
> Consequently, any subsequent call to platform_get_drvdata(pdev) 
> (which returns pdev->dev.driver_data) may yield NULL, causing a 
> crash if that pointer is dereferenced.
> 
> Fix this by adding a sanity check to ensure "hcd" is non-NULL
> before proceeding with further operations.
> 
> Reported-by: syzbot <syzbot+83976e47ec1ef91e66f1@...kaller.appspotmail.com>
> Closes: https://syzkaller.appspot.com/bug?extid=83976e47ec1ef91e66f1
> Tested-by: syzbot <syzbot+83976e47ec1ef91e66f1@...kaller.appspotmail.com>
> Fixes: 03cd00d538a6 ("usbip: vhci-hcd: Set the vhci structure up to work")
> Signed-off-by: Qasim Ijaz <qasdev00@...il.com>
> ---
>  drivers/usb/usbip/vhci_sysfs.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/usb/usbip/vhci_sysfs.c b/drivers/usb/usbip/vhci_sysfs.c
> index d5865460e82d..a5e6c3c4af06 100644
> --- a/drivers/usb/usbip/vhci_sysfs.c
> +++ b/drivers/usb/usbip/vhci_sysfs.c
> @@ -76,6 +76,10 @@ static ssize_t status_show_vhci(int pdev_nr, char *out)
>  	}
>  
>  	hcd = platform_get_drvdata(pdev);
> +

   Empty line net really needed here...

> +	if (!hcd)
> +		return 0;
> +
>  	vhci_hcd = hcd_to_vhci_hcd(hcd);
>  	vhci = vhci_hcd->vhci;
>  

MBR, Sergey