[PATCH] ugen detach race
John Baldwin
jhb at freebsd.org
Mon Apr 24 12:41:12 UTC 2006
On Saturday 22 April 2006 04:22 pm, Anish Mistry wrote:
> On Saturday 22 April 2006 14:59, Anish Mistry wrote:
> > On Wednesday 05 April 2006 04:44, Anish Mistry wrote:
> > > On Wednesday 05 April 2006 03:53, Anish Mistry wrote:
> > > > While working on getting hplip ported I ran across a race
> > > > condition in the ugen code that causes a crash. The following
> > > > patch fixes a problem where read, write, and ioctl can be
> > > > called during a detach since sc_dying isn't checked before
> > > > bumping the reference count. This puts the sc_dying check
> > > > before the *_do_* functions are called. This includes the patch
> > > > from usb/81308 to prevent polling on the control endpoint. As
> > > > well as a few NULL pointer checks from NetBSD. This patch is
> > > > applicable to RELENG_6.
> > >
> > > And CURRENT.
> > >
> > > > http://am-productions.biz/docs/ugen-detach-race.patch
> > > >
> > > > This doesn't fix the case where an application has a read/write
> > > > pending and then detach is called. In this case destroy_devl
> > > > will just keep looping until the read/write completes.
> >
> > I've updated the patch. It now includes the fix for the panic on
> > detach when a process has a device open when a detach occurs. ugen
> > now no longer waits for the process to close the connection and
> > just cuts it off.
> > Applies to RELENG_6 and CURRENT.
> >
> > http://am-productions.biz/docs/ugen-detach-race.patch
> >
> > The patch should fix usb/93949 too.
> > This seems to fix all the panics I'm seeing with the ugen device.
> > It would be nice if this could make it into 6.1.
>
> I added another panic fix. An error was introduced in rev 1.94 on
> ugen.c in the USB_SET_CONFIG ioctl case that calls
> ugen_make_devnodes. This causes a panic since this logic was moved
> to ugen_set_config a while ago. Removing the ugen_make_devnodes()
> call from ugen_do_ioctl fixes the problem. This bug made it trivial
> to cause a panic when there was access to any ugen device.
>
> http://am-productions.biz/docs/ugen-detach-race.patch
Might want to send it to freebsd-usb@ to get more usb-aware folks to review
it.
--
John Baldwin <jhb at FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve" = http://www.FreeBSD.org
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