From 2ca762790caf822f7b61430fbaffa3ae4219977f Mon Sep 17 00:00:00 2001 From: Joerg Roedel Date: Fri, 22 Jan 2010 16:45:31 +0100 Subject: [PATCH] x86/amd-iommu: Fix NULL pointer dereference in __detach_device() In the __detach_device function the reference count for a device-domain binding may become zero. This results in the device being removed from the domain and dev_data->domain will be NULL. This is bad because this pointer is dereferenced when trying to unlock the domain->lock. This patch fixes the issue by keeping the domain in a seperate variable. Signed-off-by: Joerg Roedel --- arch/x86/kernel/amd_iommu.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c index c2ccbd7b862f..4478a48198a8 100644 --- a/arch/x86/kernel/amd_iommu.c +++ b/arch/x86/kernel/amd_iommu.c @@ -1489,11 +1489,14 @@ static void __detach_device(struct device *dev) { struct iommu_dev_data *dev_data = get_dev_data(dev); struct iommu_dev_data *alias_data; + struct protection_domain *domain; unsigned long flags; BUG_ON(!dev_data->domain); - spin_lock_irqsave(&dev_data->domain->lock, flags); + domain = dev_data->domain; + + spin_lock_irqsave(&domain->lock, flags); if (dev_data->alias != dev) { alias_data = get_dev_data(dev_data->alias); @@ -1504,7 +1507,7 @@ static void __detach_device(struct device *dev) if (atomic_dec_and_test(&dev_data->bind)) do_detach(dev); - spin_unlock_irqrestore(&dev_data->domain->lock, flags); + spin_unlock_irqrestore(&domain->lock, flags); /* * If we run in passthrough mode the device must be assigned to the