On Tue, Sep 22, 2020 at 12:40:42PM +0200, Oliver Neukum wrote:
> Am Dienstag, den 22.09.2020, 09:05 +0200 schrieb Johan Hovold:
>
> > The relevant commits are
> >
> > a2bfb4a346d2 ("USB: support for cdc-acm of single interface devices") (2009)
> > fd5054c169d2 ("USB: cdc_acm: Fix oops when Droids MuIn LCD is connected") (2011)
> > 403dff4e2c94 ("USB: cdc-acm: check for valid interfaces") (2014)
> >
> > Before Greg added the sanity checks in that last commit, a broken
> > call-management descriptor referring to a non-existent interface would
> > cause a NULL-pointer dereference.
>
> Yes.
>
> > The second commit, adding support for a specific device, didn't fix that
> > problem generally
>
> Yes
>
> > and only worked around it for one device by hardcoding
> > the data interface to match the control interface,
>
> How do you know. It hardcoded the data interface. That it matches
> the control interface is a guess.
No, see below.
> > thereby falling back
> > to the "combined-interface" probing you added in that first commit.
>
> How do you know? They may or may not match.
Heh. Did you actually read the commit message?
"Add NO_DATA_INTERFACE quirk to tell the driver that "control"
and "data" interfaces are not separated for this device, which
prevents dereferencing a null pointer in the device probe
code."
Convinced yet?
Johan
