linux-kernel - [PATCH 8/16][BUG] PCI slot: Fix invalid memory access (Not for mainline!)

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Date:	Fri, 21 Mar 2008 13:15:45 +0900
From:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
To:	Alex Chiang <achiang@...com>, Greg KH <gregkh@...e.de>
CC:	Gary Hade <garyhade@...ibm.com>,
	Kristen Carlson Accardi <kristen.c.accardi@...el.com>,
	Matthew Wilcox <matthew@....cx>, warthog19@...lescrag.net,
	rick.jones2@...com, linux-kernel@...r.kernel.org,
	linux-pci@...ey.karlin.mff.cuni.cz, linux-acpi@...r.kernel.org
Subject: [PATCH  8/16][BUG] PCI slot: Fix invalid memory access (Not for mainline!)

Fix kernel oops in pci_release_slot() when dbg() is enabled.

The dbg() in pci_release_slot() cause a kernel oops (invalid memory
access) because it accesses slot after it is released. We need to
access slot before calling kobject_put().

Signed-off-by: Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>

---
 drivers/pci/slot.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

Index: linux-2.6.25-rc6/drivers/pci/slot.c
===================================================================
--- linux-2.6.25-rc6.orig/drivers/pci/slot.c
+++ linux-2.6.25-rc6/drivers/pci/slot.c
@@ -191,13 +191,14 @@ EXPORT_SYMBOL_GPL(pci_create_slot);
 
 int pci_destroy_slot(struct pci_slot *slot)
 {
+	dbg("%s: decreased refcount to %d on %x:%d\n", __func__,
+	    atomic_read(&slot->kobj.kref.refcount) - 1, slot->bus->number,
+	    slot->number);
+
 	down_write(&pci_bus_sem);
 	kobject_put(&slot->kobj);
 	up_write(&pci_bus_sem);
 
-	dbg("%s: decreased refcount to %d on %x:%d\n", __func__,
-	    atomic_read(&slot->kobj.kref.refcount), slot->bus->number,
-	    slot->number);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(pci_destroy_slot);


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