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

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Message-ID: <Z5DjS7M6YQ7q-rBO@qasdev.system>
Date: Wed, 22 Jan 2025 12:23:39 +0000
From: Qasim Ijaz <qasdev00@...il.com>
To: Sergey Shtylyov <sergei.shtylyov@...il.com>
Cc: valentina.manea.m@...il.com, shuah@...nel.org, i@...ithal.me,
	gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] USB: usbip: fix null-ptr-deref in status_show_vhci()

On Wed, Jan 22, 2025 at 11:56:34AM +0300, Sergey Shtylyov wrote:
> 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...

Thanks for spotting this Sergey. Just send out patch v2 which fixes
this.

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