Re: [PATCH] usb: gadget: net2280: fix NULL pointer dereference

[Alan Stern]

On Thu, Mar 16, 2023 at 05:19:35PM +0100, Greg Kroah-Hartman wrote:
> On Thu, Mar 16, 2023 at 06:53:55PM +0300, Valery Zabrovsky wrote:
> > In net2280_free_request():
> > If _ep is NULL, then ep is NULL and is dereferenced
> > while trying to produce an error message.
> 
> How can that ever happen?  How did you test and hit this?
> 
> > The patch replaces dev_err() with pr_err() which works fine.
> 
> That's not a good idea for driver code to use, sorry.
> 
> > Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> As I have said before, your testing framework needs a lot more work.
> 
> good luck!

In situations like this, it might be better to remove the check 
entirely.  If a driver does pass a NULL pointer, it will lead to an 
invalid pointer dereference which will certainly cause an oops and might 
very well crash the system.  That would be a lot more noticeable than an 
error message hidden in a kernel log!

Greg, is there any general policy about the need for sanity checks such 
as this one?  Like, don't put them in whenever a failure would lead 
to an immediate fault which would be easy to track down?

Alan Stern