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SubjectRe: [PATCH] usb: gadget: net2280: fix NULL pointer dereference
On Thu, Mar 16, 2023 at 02:22:35PM -0400, Alan Stern wrote:
> 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?

That's the policy, no need to check if a caller is abusing the code and
will find out instantly. Otherwise we end up checking on every
function, and that way lies madness.

thanks,

greg k-h

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