patch "mei: bus: need to unlink client before freeing" added to char-misc-linus

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    mei: bus: need to unlink client before freeing

to my char-misc git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-linus branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.

If you have any questions about this process, please let me know.


>From 34f1166afd67f9f48a08c52f36180048908506a4 Mon Sep 17 00:00:00 2001
From: Tomas Winkler <tomas.winkler@intel.com>
Date: Mon, 27 Aug 2018 22:40:16 +0300
Subject: mei: bus: need to unlink client before freeing
MIME-Version: 1.0
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In case a client fails to connect in mei_cldev_enable(), the
caller won't call the mei_cldev_disable leaving the client
in a linked stated. Upon driver unload the client structure
will be freed in  mei_cl_bus_dev_release(), leaving a stale pointer
on a fail_list.  This will eventually end up in crash
during power down flow in mei_cl_set_disonnected().

RIP:  mei_cl_set_disconnected+0x5/0x260[mei]
Call trace:
mei_cl_all_disconnect+0x22/0x30
mei_reset+0x194/0x250
__synchronize_hardirq+0x43/0x50
_cond_resched+0x15/0x30
mei_me_intr_clear+0x20/0x100
mei_stop+0x76/0xb0
mei_me_shutdown+0x3f/0x80
pci_device_shutdown+0x34/0x60
kernel_restart+0x0e/0x30

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=200455
Fixes: 'c110cdb17148 ("mei: bus: make a client pointer always available")'
Cc: <stable@vger.kernel.org> 4.10+
Tested-by: Georg Müller <georgmueller@gmx.net>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/misc/mei/bus.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/misc/mei/bus.c b/drivers/misc/mei/bus.c
index 13c6c9a2248a..fc3872fe7b25 100644
--- a/drivers/misc/mei/bus.c
+++ b/drivers/misc/mei/bus.c
@@ -521,17 +521,15 @@ int mei_cldev_enable(struct mei_cl_device *cldev)
 
 	cl = cldev->cl;
 
+	mutex_lock(&bus->device_lock);
 	if (cl->state == MEI_FILE_UNINITIALIZED) {
-		mutex_lock(&bus->device_lock);
 		ret = mei_cl_link(cl);
-		mutex_unlock(&bus->device_lock);
 		if (ret)
-			return ret;
+			goto out;
 		/* update pointers */
 		cl->cldev = cldev;
 	}
 
-	mutex_lock(&bus->device_lock);
 	if (mei_cl_is_connected(cl)) {
 		ret = 0;
 		goto out;
@@ -875,12 +873,13 @@ static void mei_cl_bus_dev_release(struct device *dev)
 
 	mei_me_cl_put(cldev->me_cl);
 	mei_dev_bus_put(cldev->bus);
+	mei_cl_unlink(cldev->cl);
 	kfree(cldev->cl);
 	kfree(cldev);
 }
 
 static const struct device_type mei_cl_device_type = {
-	.release	= mei_cl_bus_dev_release,
+	.release = mei_cl_bus_dev_release,
 };
 
 /**
-- 
2.18.0