Quoting Alan Stern (stern@xxxxxxxxxxxxxxxxxxx):
> On Fri, 16 Dec 2011, Sarah Sharp wrote:
>
> > When running the Point Grey "flycap" program for their USB 3.0 camera
> > (which was running as a USB 2.0 device for some reason), I trigger this
> > oops whenever I try to open a video stream:
> ...
> > markup_oops.pl says the oops is in put_cred:
> ...
>
> > This bug seems to have been introduced by commit
> > d178bc3a708f39cbfefc3fab37032d3f2511b4ec "user namespace: usb: make usb
> > urbs user namespace aware (v2)"
> >
> > I'm not sure if this is right fix, but it does stop the oops.
> >
> > Unfortunately, the Point Grey software still refuses to work, but it's a
> > closed source app, so I can't fix it.
> >
> > Signed-off-by: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx>
> > Cc: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx>
Thanks, Sarah.
Acked-by: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx>
> > ---
> > drivers/usb/core/devio.c | 3 ++-
> > 1 files changed, 2 insertions(+), 1 deletions(-)
> >
> > diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
> > index d8cf06f..3af5e2d 100644
> > --- a/drivers/usb/core/devio.c
> > +++ b/drivers/usb/core/devio.c
> > @@ -286,7 +286,8 @@ static struct async *alloc_async(unsigned int numisoframes)
> > static void free_async(struct async *as)
> > {
> > put_pid(as->pid);
> > - put_cred(as->cred);
> > + if (as->cred)
> > + put_cred(as->cred);
> > kfree(as->urb->transfer_buffer);
> > kfree(as->urb->setup_packet);
> > usb_free_urb(as->urb);
>
> This is a reasonable fix. It turns out there are a couple of error
> paths by which a struct async can be freed before its .cred member has
> been set. The alternative fix is to move the statement initializing
> as->cred up earlier, before those errors occur. But what you did is
> probably more robust.
>
> The most likely error, which didn't exist when commit d178bc3a708f39
> was written, is that the usbfs memory limit was exceeded. You can see
> if increasing that limit helps "flycap" at all. (The other error path
> happens when kmalloc fails to get enough memory for the URB's transfer
> buffer.)
>
> Alan Stern
>
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