linux-kernel - [21/27] firewire: sbp2: fix panic after rmmod with slow targets

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Date:	Sun, 23 Oct 2011 08:24:49 +0200
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	stable-review@...r.kernel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Chris Boot <bootc@...tc.net>,
	Stefan Richter <stefanr@...6.in-berlin.de>
Subject: [21/27] firewire: sbp2: fix panic after rmmod with slow targets

3.0-stable review patch.  If anyone has any objections, please let us know.

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

From: Chris Boot <bootc@...tc.net>

commit 0278ccd9d53e07c4e699432b2fed9de6c56f506c upstream.

If firewire-sbp2 starts a login to a target that doesn't complete ORBs
in a timely manner (and has to retry the login), and the module is
removed before the operation times out, you end up with a null-pointer
dereference and a kernel panic.

[SR:  This happens because sbp2_target_get/put() do not maintain
module references.  scsi_device_get/put() do, but at occasions like
Chris describes one, nobody holds a reference to an SBP-2 sdev.]

This patch cancels pending work for each unit in sbp2_remove(), which
hopefully means there are no extra references around that prevent us
from unloading. This fixes my crash.

Signed-off-by: Chris Boot <bootc@...tc.net>
Signed-off-by: Stefan Richter <stefanr@...6.in-berlin.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/firewire/sbp2.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/firewire/sbp2.c
+++ b/drivers/firewire/sbp2.c
@@ -1198,6 +1198,10 @@ static int sbp2_remove(struct device *de
 {
 	struct fw_unit *unit = fw_unit(dev);
 	struct sbp2_target *tgt = dev_get_drvdata(&unit->device);
+	struct sbp2_logical_unit *lu;
+
+	list_for_each_entry(lu, &tgt->lu_list, link)
+		cancel_delayed_work_sync(&lu->work);

 	sbp2_target_put(tgt);
 	return 0;

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