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Commit60f030f741("iommu/vt-d: Avoid use of NULL after WARN_ON_ONCE") fixed a NULL pointer dereference in an unlikely situation partly. If dev_pasid is not found in the dev_pasids list, it remains NULL. However, the teardown operations are executed unconditionally, this lead to a NULL pointer dereference or refcount corruption. If the domain was never attached to this IOMMU, info will be NULL, which would cause an immediate dereference when checking --info->refcnt. Even if info is not NULL, decrementing the refcount without having removed a valid PASID might unbalance the count. This could lead to premature dropping of the refcount to 0, potentially causing a use-after-free for the remaining active devices sharing the domain. Fix it by returning early if dev_pasid is NULL, before executing the teardown operations. Issue found by AI review and suggested by Kevin Tian. https://sashiko.dev/#/patchset/20260421031347.1408890-1-zhenzhong.duan%40intel.com Fixes:60f030f741("iommu/vt-d: Avoid use of NULL after WARN_ON_ONCE") Cc: stable@vger.kernel.org Suggested-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com> Reviewed-by: Kevin Tian <kevin.tian@intel.com> Link: https://lore.kernel.org/r/20260422033538.95000-1-zhenzhong.duan@intel.com Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com> Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>