[3.16.y-ckt extended stable] Patch "PM / clk: Fix crash in clocks management code if !CONFIG_PM_RUNTIME" has been added to staging queue

[Luis Henriques]

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

    PM / clk: Fix crash in clocks management code if !CONFIG_PM_RUNTIME

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt1.

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

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 5b79f141aaa9fb98dda75f70dce2f3e6f632daf3 Mon Sep 17 00:00:00 2001
From: Geert Uytterhoeven <geert+renesas at glider.be>
Date: Wed, 1 Oct 2014 20:38:17 +0200
Subject: PM / clk: Fix crash in clocks management code if !CONFIG_PM_RUNTIME

commit a968bed78b549b4c61d4a46e59161fc1f60f96a6 upstream.

Unlike the clocks management code for runtime PM, the code used for
system suspend does not check the pm_clock_entry.status field.
If pm_clk_acquire() failed, ce->status will be PCE_STATUS_ERROR, and
ce->clk will be a negative error code (e.g. 0xfffffffe = -2 = -ENOENT).

Depending on the clock implementation, suspend or resume may crash with:

    Unable to handle kernel NULL pointer dereference at virtual address 00000026

(CCF clk_disable() has an IS_ERR_OR_NULL() check, while CCF clk_enable()
 only has a NULL check; pre-CCF implementations may behave differently)

While just checking for PCE_STATUS_ERROR would be sufficient, it doesn't
hurt to use the same state machine as is done for runtime PM, as this
makes the two versions more similar, and eligible for a future
consolidation.

Signed-off-by: Geert Uytterhoeven <geert+renesas at glider.be>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/base/power/clock_ops.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/base/power/clock_ops.c b/drivers/base/power/clock_ops.c
index b99e6c06ee67..78369305e069 100644
--- a/drivers/base/power/clock_ops.c
+++ b/drivers/base/power/clock_ops.c
@@ -368,8 +368,13 @@ int pm_clk_suspend(struct device *dev)

 	spin_lock_irqsave(&psd->lock, flags);

-	list_for_each_entry_reverse(ce, &psd->clock_list, node)
-		clk_disable(ce->clk);
+	list_for_each_entry_reverse(ce, &psd->clock_list, node) {
+		if (ce->status < PCE_STATUS_ERROR) {
+			if (ce->status == PCE_STATUS_ENABLED)
+				clk_disable(ce->clk);
+			ce->status = PCE_STATUS_ACQUIRED;
+		}
+	}

 	spin_unlock_irqrestore(&psd->lock, flags);

@@ -385,6 +390,7 @@ int pm_clk_resume(struct device *dev)
 	struct pm_subsys_data *psd = dev_to_psd(dev);
 	struct pm_clock_entry *ce;
 	unsigned long flags;
+	int ret;

 	dev_dbg(dev, "%s()\n", __func__);

@@ -394,8 +400,13 @@ int pm_clk_resume(struct device *dev)

 	spin_lock_irqsave(&psd->lock, flags);

-	list_for_each_entry(ce, &psd->clock_list, node)
-		__pm_clk_enable(dev, ce->clk);
+	list_for_each_entry(ce, &psd->clock_list, node) {
+		if (ce->status < PCE_STATUS_ERROR) {
+			ret = __pm_clk_enable(dev, ce->clk);
+			if (!ret)
+				ce->status = PCE_STATUS_ENABLED;
+		}
+	}

 	spin_unlock_irqrestore(&psd->lock, flags);

--
2.1.0