linux-kernel - Re: [PATCH] USB: serial: Fix use after free in debug printk

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Message-ID: <490dc872-fc62-49da-89ff-4eba067df8c0@stanley.mountain>
Date: Thu, 31 Oct 2024 12:39:10 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Johan Hovold <johan@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] USB: serial: Fix use after free in debug printk

On Thu, Oct 31, 2024 at 12:35:31PM +0300, Dan Carpenter wrote:
> On Thu, Oct 31, 2024 at 10:07:42AM +0100, Johan Hovold wrote:
> > On Thu, Oct 31, 2024 at 09:59:10AM +0300, Dan Carpenter wrote:
> > > The dev_dbg() call dereferences "urb" but it was already freed on the
> > > previous line.  Move the debug output earlier in the function.
> > 
> > Thanks for catching this, but please use a temporary variable for the
> > struct device pointer instead of changing the flow.
> > 
> 
> Why?  The output is the same either way and this way is cleaner code.
> 

Nah, you're right.  A temporary variable is nicer.  It avoids having two if
statements.

regards,
dan carpenter