[ 3.5.y.z extended stable ] Patch "ACPI / PNP: Do not crash due to stale pointer use during" has been added to staging queue

[Herton Ronaldo Krzesinski]

This is a note to let you know that I have just added a patch titled

    ACPI / PNP: Do not crash due to stale pointer use during

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Herton

------

>From 0deef1289c0257f21190fe53801a498f6305b615 Mon Sep 17 00:00:00 2001
From: "Rafael J. Wysocki" <rafael.j.wysocki at intel.com>
Date: Fri, 30 Nov 2012 13:05:05 +0100
Subject: [PATCH] ACPI / PNP: Do not crash due to stale pointer use during
 system resume

commit a6b5e88c0e42093b9057856f35770966c8c591e3 upstream.

During resume from system suspend the 'data' field of
struct pnp_dev in pnpacpi_set_resources() may be a stale pointer,
due to removal of the associated ACPI device node object in the
previous suspend-resume cycle.  This happens, for example, if a
dockable machine is booted in the docking station and then suspended
and resumed and suspended again.  If that happens,
pnpacpi_build_resource_template() called from pnpacpi_set_resources()
attempts to use that pointer and crashes.

However, pnpacpi_set_resources() actually checks the device's ACPI
handle, attempts to find the ACPI device node object attached to it
and returns an error code if that fails, so in fact it knows what the
correct value of dev->data should be.  Use this observation to update
dev->data with the correct value if necessary and dump a call trace
if that's the case (once).

We still need to fix the root cause of this issue, but preventing
systems from crashing because of it is an improvement too.

Reported-and-tested-by: Zdenek Kabelac <zdenek.kabelac at gmail.com>
References: https://bugzilla.kernel.org/show_bug.cgi?id=51071
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 drivers/pnp/pnpacpi/core.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/pnp/pnpacpi/core.c b/drivers/pnp/pnpacpi/core.c
index d21e8f5..e353788 100644
--- a/drivers/pnp/pnpacpi/core.c
+++ b/drivers/pnp/pnpacpi/core.c
@@ -95,6 +95,9 @@ static int pnpacpi_set_resources(struct pnp_dev *dev)
 		return -ENODEV;
 	}

+	if (WARN_ON_ONCE(acpi_dev != dev->data))
+		dev->data = acpi_dev;
+
 	ret = pnpacpi_build_resource_template(dev, &buffer);
 	if (ret)
 		return ret;
--
1.7.9.5