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iommu/amd: Fix NULL pointer dereference for GPUs without upstream bridge

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pci_upstream_bridge() can return NULL for devices without an upstream
bridge. The AMD GPU identity mapping quirk dereferences the returned
pointer unconditionally, causing a kernel panic during boot.

Check the pointer before accessing the bridge vendor ID.

This fixes a boot regression on a Lenovo system with an AMD PRO
A10-9700E APU. The system now boots with AMD IOMMU enabled.

Fixes: bf5bdfd1f8 ("iommu/amd: Force identity mode for selected GPUs only")

Signed-off-by: Jean-Christophe Guillain <jean-christophe@guillain.net>
Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
This commit is contained in:
Jean-Christophe Guillain 2026-11-05 16:32:19 +00:00 committed by Joerg Roedel
parent fa77b023eb
commit 2cf4be57b3
1 changed files with 3 additions and 1 deletions
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4
drivers/iommu/amd/iommu.c
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@ -3191,6 +3191,7 @@ static bool amd_iommu_is_attach_deferred(struct device *dev)
static bool quirks_force_identity_mapping(struct pci_dev *pdev)
{
struct pci_dev *bridge;
int class = pdev->class >> 8;
/* AMD GPU vendor ID */
@ -3202,7 +3203,8 @@ static bool quirks_force_identity_mapping(struct pci_dev *pdev)
class != PCI_CLASS_DISPLAY_OTHER)
return false;
if (pci_upstream_bridge(pdev)->vendor == PCI_VENDOR_ID_ATI)
bridge = pci_upstream_bridge(pdev);
if (bridge && bridge->vendor == PCI_VENDOR_ID_ATI)
return false;
/* It is the GPU in an APU, force identity domain */