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Re: kern/50810: Kernel page fault trap in ugenclose()
The following reply was made to PR kern/50810; it has been noted by GNATS.
From: Andreas Gustafsson <gson%gson.org@localhost>
Subject: Re: kern/50810: Kernel page fault trap in ugenclose()
Date: Sat, 20 Feb 2016 13:11:39 +0200
Nick Hudson wrote:
> The ioctl (USB_SET_ALTINTERFACE) is blatting edesc and making it fail
> Not sure why it's doing this before closing the endpoints.
> Maybe the ioctl should fail here?
I'm having some trouble following your comment.
- What do you mean by "blatting"? The dictionary
I consulted was not helpful.
- In "why it's doing this", what does "it" refer to?
- At what point should the ioctl fail, and why would it make
I see there is a comment in ugen_set_interface() saying /* XXX should
only do this after setting new altno has succeeded */, which seems to
point at a possible cause of the bug: If setting the new altno fails,
sce->edesc will be NULL, but sce->pipeh has not been cleared, so if it
was not NULL to begin, with we have the exact combination of
conditions (sce->pipeh != NULL && sce->edesc == NULL) that triggers
the crash in ugenclose().
Also, there are several places checking for sce == NULL, for example:
sce = &sc->sc_endpoints[UGENENDPOINT(dev)][IN];
if (sce == NULL)
None of these make any sense - sce is a pointer into the middle of a
the ugen_softc struct, so it can *never* be NULL by definition.
Should they all say "sce->sc == NULL"? What is the canonical way
of distinguishing a valid endpoint from an invalid one?
Andreas Gustafsson, gson%gson.org@localhost
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