From 5a244727f428a06634f22bb890e78024ab0c89f3 Mon Sep 17 00:00:00 2001
From: William Breathitt Gray <vilhelm.gray@gmail.com>
Date: Wed, 8 Nov 2017 10:23:11 -0500
Subject: [PATCH] isa: Prevent NULL dereference in isa_bus driver callbacks
Git-commit: 5a244727f428a06634f22bb890e78024ab0c89f3
Patch-mainline: v4.15-rc3
References: bsc#1051510

The isa_driver structure for an isa_bus device is stored in the device
platform_data member of the respective device structure. This
platform_data member may be reset to NULL if isa_driver match callback
for the device fails, indicating a device unsupported by the ISA driver.

This patch fixes a possible NULL pointer dereference if one of the
isa_driver callbacks to attempted for an unsupported device. This error
should not occur in practice since ISA devices are typically manually
configured and loaded by the users, but we may as well prevent this
error from popping up for the 0day testers.

Fixes: a5117ba7da37 ("[PATCH] Driver model: add ISA bus")
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Cc: stable <stable@vger.kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/base/isa.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

--- a/drivers/base/isa.c
+++ b/drivers/base/isa.c
@@ -39,7 +39,7 @@ static int isa_bus_probe(struct device *
 {
 	struct isa_driver *isa_driver = dev->platform_data;
 
-	if (isa_driver->probe)
+	if (isa_driver && isa_driver->probe)
 		return isa_driver->probe(dev, to_isa_dev(dev)->id);
 
 	return 0;
@@ -49,7 +49,7 @@ static int isa_bus_remove(struct device
 {
 	struct isa_driver *isa_driver = dev->platform_data;
 
-	if (isa_driver->remove)
+	if (isa_driver && isa_driver->remove)
 		return isa_driver->remove(dev, to_isa_dev(dev)->id);
 
 	return 0;
@@ -59,7 +59,7 @@ static void isa_bus_shutdown(struct devi
 {
 	struct isa_driver *isa_driver = dev->platform_data;
 
-	if (isa_driver->shutdown)
+	if (isa_driver && isa_driver->shutdown)
 		isa_driver->shutdown(dev, to_isa_dev(dev)->id);
 }
 
@@ -67,7 +67,7 @@ static int isa_bus_suspend(struct device
 {
 	struct isa_driver *isa_driver = dev->platform_data;
 
-	if (isa_driver->suspend)
+	if (isa_driver && isa_driver->suspend)
 		return isa_driver->suspend(dev, to_isa_dev(dev)->id, state);
 
 	return 0;
@@ -77,7 +77,7 @@ static int isa_bus_resume(struct device
 {
 	struct isa_driver *isa_driver = dev->platform_data;
 
-	if (isa_driver->resume)
+	if (isa_driver && isa_driver->resume)
 		return isa_driver->resume(dev, to_isa_dev(dev)->id);
 
 	return 0;