linux-kernel - Re: [PATCH] usb: core: don't try to reset_device() a port that got just disconnected

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAODwPW8ZRpVPWKp0Eda4GDhNHiBqcWECW7d69H_oi4UoFQL_NQ@mail.gmail.com>
Date:	Tue, 30 Jul 2013 19:33:46 -0700
From:	Julius Werner <jwerner@...omium.org>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Julius Werner <jwerner@...omium.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	LKML <linux-kernel@...r.kernel.org>, linux-usb@...r.kernel.org,
	Sarah Sharp <sarah.a.sharp@...ux.intel.com>,
	Vincent Palatin <vpalatin@...omium.org>,
	Benson Leung <bleung@...omium.org>
Subject: Re: [PATCH] usb: core: don't try to reset_device() a port that got
 just disconnected

> Wait a moment.  Why does each of these attempts lead to a 5-second
> timeout?  Why don't they fail immediately?

Now that you mention it, that's a very good question. The kernel
enqueues a control transfer to the now disconnected address because
it's internal bookkeeping is not yet updated, but I guess that should
usually fail very fast from an xHC-internal transaction timeout. I
have now tried to debug the cause of this: I see the transfer being
enqueued and the doorbell triggered, but never get a transfer event
back from it (until the software timeout calls usb_kill_urb() which
stops the endpoint). With the same setup on a PantherPoint system I
get the same U1/U2 disable control messages on unplugging, but they
fail within <5ms with a transaction error... so I guess this must be a
LynxPoint hardware bug.

Regardless, calling usb_reset_device() is still wrong and will at
least lead to pointless transfer attempts and error messages, so I
think my patch still has merit.

> What will happen here if udev is NULL?  Maybe you should change the
> test to (!udev || !(portstatus & ...)).

Right... I'm not sure if that can happen in practice, but I'll change
it just in case.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/