linux-kernel - [PATCH] base/platform: fix panic when probe function is NULL

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Date:	Thu, 26 Nov 2015 20:01:34 +0100
From:	martin.wilck@...fujitsu.com
To:	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org
Cc:	u.kleine-koenig@...gutronix.de, tpmdd-devel@...ts.sourceforge.net,
	Martin Wilck <Martin.Wilck@...fujitsu.com>
Subject: [PATCH] base/platform: fix panic when probe function is NULL

From: Martin Wilck <Martin.Wilck@...fujitsu.com>

Since b8b2c7d845d5, platform_drv_probe() is called for all platform
devices. If drv->probe is NULL, and dev_pm_domain_attach() fails,
platform_drv_probe() will return the error code from dev_pm_domain_attach().

This causes real_probe() to enter the "probe_failed" path and set
dev->driver to NULL. Before b8b2c7d845d5, real_probe() would assume
success if both dev->bus->probe and drv->probe are missing.

This may cause a panic later. For example, inserting the tpm_tis
driver with parameter "force=1" (i.e. registering tpm_tis as a platform
driver) will panic in tpmm_chip_alloc() because dev->driver is NULL:

     chip->cdev.owner = chip->pdev->driver->owner;

This patch fixes this by returning success in platform_drv_probe() if
"just" dev_pm_domain_attach() had failed. This restores the semantics
of platform_device_register_XXX() if the associated platform driver has
no "probe" function.

Fixes: b8b2c7d845d5 ("base/platform: assert that dev_pm_domain
callbacks are called unconditionally")

Signed-off-by: Martin Wilck <Martin.Wilck@...fujitsu.com>
---
 drivers/base/platform.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index 1dd6d3b..c994e76 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -513,10 +513,14 @@ static int platform_drv_probe(struct device *_dev)
 		return ret;

 	ret = dev_pm_domain_attach(_dev, true);
-	if (ret != -EPROBE_DEFER && drv->probe) {
-		ret = drv->probe(dev);
-		if (ret)
-			dev_pm_domain_detach(_dev, true);
+	if (ret != -EPROBE_DEFER) {
+		if (drv->probe) {
+			ret = drv->probe(dev);
+			if (ret)
+				dev_pm_domain_detach(_dev, true);
+		} else
+			/* don't fail if just dev_pm_domain_attach failed */
+			ret = 0;
 	}

 	if (drv->prevent_deferred_probe && ret == -EPROBE_DEFER) {
-- 
1.8.3.1

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