Fwd: Re: [PATCH] ugen detach race

[Anish Mistry]

Sending to the usb list as per jhb's suggestion.

----------  Forwarded Message  ----------

Subject: Re: [PATCH] ugen detach race
Date: Saturday 22 April 2006 16:22
From: Anish Mistry <mistry.7 at osu.edu>
To: freebsd-current at freebsd.org
Cc: Ian Dowse <iedowse at freebsd.org>

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

--
Anish Mistry

-------------------------------------------------------

-- 
Anish Mistry
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