[PATCH 3/3] pm: domains: avoid potential oops in pm_genpd_remove_device()

[Russell King <rmk+kernel@arm.linux.org.uk>]

pm_genpd_remove_device() tries hard to validate the generic PM domain
passed to it, but the validation is not complete.

dev->pm_domain contains a struct dev_pm_domain, which is the "base
class" of generic PM domains.  Other users of dev_pm_domains include
stuff like vga_switheroo.  Hence, a device could have a generic PM
domain or a vga_switcheroo PM domain in dev->pm_domain.

We need ot be certain that the PM domain is actually valid before we
try to remove it.  We can do this easily as we have a way to get the
current validated generic PM domain for a struct device.  This must
match the generic PM domain being requested for removal.

Convert the code to use this alternative validation method instead.

Acked-by: Kevin Hilman <khilman@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
 drivers/base/power/domain.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 89d2eea7f561..5f560fa45a32 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -1538,9 +1538,7 @@ int pm_genpd_remove_device(struct generic_pm_domain *genpd,
 
 	dev_dbg(dev, "%s()\n", __func__);
 
-	if (IS_ERR_OR_NULL(genpd) || IS_ERR_OR_NULL(dev)
-	    ||  IS_ERR_OR_NULL(dev->pm_domain)
-	    ||  pd_to_genpd(dev->pm_domain) != genpd)
+	if (!genpd || genpd != pm_genpd_lookup_dev(dev))
 		return -EINVAL;
 
 	genpd_acquire_lock(genpd);
-- 
1.8.3.1