From 79ea2feb917b05366b49d85573c9c5331f043b2c Mon Sep 17 00:00:00 2001 From: Zhenzhong Duan Date: Sat, 9 May 2026 10:43:46 +0800 Subject: [PATCH] iommu/vt-d: Avoid NULL pointer dereference or refcount corruption Commit 60f030f7418d ("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: 60f030f7418d ("iommu/vt-d: Avoid use of NULL after WARN_ON_ONCE") Cc: stable@vger.kernel.org Suggested-by: Kevin Tian Signed-off-by: Zhenzhong Duan Reviewed-by: Kevin Tian Link: https://lore.kernel.org/r/20260422033538.95000-1-zhenzhong.duan@intel.com Signed-off-by: Lu Baolu Signed-off-by: Joerg Roedel --- drivers/iommu/intel/iommu.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c index a4b123c33022..4d0e65bc131d 100644 --- a/drivers/iommu/intel/iommu.c +++ b/drivers/iommu/intel/iommu.c @@ -3545,12 +3545,13 @@ void domain_remove_dev_pasid(struct iommu_domain *domain, } spin_unlock_irqrestore(&dmar_domain->lock, flags); + if (WARN_ON_ONCE(!dev_pasid)) + return; + cache_tag_unassign_domain(dmar_domain, dev, pasid); domain_detach_iommu(dmar_domain, iommu); - if (!WARN_ON_ONCE(!dev_pasid)) { - intel_iommu_debugfs_remove_dev_pasid(dev_pasid); - kfree(dev_pasid); - } + intel_iommu_debugfs_remove_dev_pasid(dev_pasid); + kfree(dev_pasid); } static int blocking_domain_set_dev_pasid(struct iommu_domain *domain,