[PATCH 2/5] x86/amd-iommu: Fix NULL pointer dereference in __detach_device()

From: Joerg Roedel
Date: Fri Jan 22 2010 - 12:19:30 EST

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

Signed-off-by: Joerg Roedel <joerg.roedel@xxxxxxx>
arch/x86/kernel/amd_iommu.c | 7 +++++--
1 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c
index c2ccbd7..4478a48 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;


- 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))

- 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

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