FAILED: patch "[PATCH] iommufd: Fail replace if device has not been attached" failed to apply to 6.12-stable tree

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 55c85fa7579dc2e3f5399ef5bad67a44257c1a48
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025041701-aerospace-retired-ff75@gregkh' --subject-prefix 'PATCH 6.12.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 55c85fa7579dc2e3f5399ef5bad67a44257c1a48 Mon Sep 17 00:00:00 2001
From: Yi Liu <[email protected]>
Date: Wed, 5 Mar 2025 19:48:42 -0800
Subject: [PATCH] iommufd: Fail replace if device has not been attached

The current implementation of iommufd_device_do_replace() implicitly assumes that the input device has already been attached. However, there is no explicit check to verify this assumption. If another device within the same group has been attached, the replace operation might succeed, but the input device itself may not have been attached yet.

As a result, the input device might not be tracked in the igroup->device_list, and its reserved IOVA might not be added. Despite this, the caller might incorrectly assume that the device has been successfully replaced, which could lead to unexpected behavior or errors.

To address this issue, add a check to ensure that the input device has been attached before proceeding with the replace operation. This check will help maintain the integrity of the device tracking system and prevent potential issues arising from incorrect assumptions about the device's attachment status.

index b2f0cb909e6d..bd50146e2ad0 100644
@@ -471,6 +471,17 @@ iommufd_device_attach_reserved_iova(struct iommufd_device *idev,
 
 /* The device attach/detach/replace helpers for attach_handle */
 
+/* Check if idev is attached to igroup->hwpt */
+static bool iommufd_device_is_attached(struct iommufd_device *idev)
+{
+	struct iommufd_device *cur;
+
+	list_for_each_entry(cur, &idev->igroup->device_list, group_item)
+		if (cur == idev)
+			return true;
+	return false;
+}
+
 static int iommufd_hwpt_attach_device(struct iommufd_hw_pagetable *hwpt,
 				      struct iommufd_device *idev)
 {

@@ -710,6 +721,11 @@ iommufd_device_do_replace(struct iommufd_device *idev,
 		goto err_unlock;
 	}
 
+	if (!iommufd_device_is_attached(idev)) {
+		rc = -EINVAL;
+		goto err_unlock;
+	}
+
 	if (hwpt == igroup->hwpt) {
 		mutex_unlock(&idev->igroup->lock);
 		return NULL;

The current implementation of iommufd_device_do_replace() implicitly assumes that the input device has already been attached. However, there is no explicit check to verify this assumption. If another device within the same group has been attached, the replace operation might succeed, but the input device itself may not have been attached yet.

As a result, the input device might not be tracked in the igroup->device_list, and its reserved IOVA might not be added. Despite this, the caller might incorrectly assume that the device has been successfully replaced, which could lead to unexpected behavior or errors.

To address this issue, add a check to ensure that the input device has been attached before proceeding with the replace operation. This check will help maintain the integrity of the device tracking system and prevent potential issues arising from incorrect assumptions about the device's attachment status.

---
 drivers/iommu/iommufd/device.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

index 5fd3dd420290..0d9786d86e3e 100644
@@ -352,6 +352,19 @@ iommufd_device_attach_reserved_iova(struct iommufd_device *idev,
 	return 0;
 }
 
+/* The device attach/detach/replace helpers for attach_handle */
+
+/* Check if idev is attached to igroup->hwpt */
+static bool iommufd_device_is_attached(struct iommufd_device *idev)
+{
+	struct iommufd_device *cur;
+
+	list_for_each_entry(cur, &idev->igroup->device_list, group_item)
+		if (cur == idev)
+			return true;
+	return false;
+}
+
 int iommufd_hw_pagetable_attach(struct iommufd_hw_pagetable *hwpt,
 				struct iommufd_device *idev)
 {

@@ -488,6 +501,11 @@ iommufd_device_do_replace(struct iommufd_device *idev,
 		goto err_unlock;
 	}
 
+	if (!iommufd_device_is_attached(idev)) {
+		rc = -EINVAL;
+		goto err_unlock;
+	}
+
 	if (hwpt == igroup->hwpt) {
 		mutex_unlock(&idev->igroup->lock);
 		return NULL;

2.34.1

[ Sasha's backport helper bot ]

Hi,

Summary of potential issues:
⚠️ Found matching upstream commit but patch is missing proper reference to it

Found matching upstream commit: 55c85fa7579dc2e3f5399ef5bad67a44257c1a48

Status in newer kernel trees:
6.14.y | Not found
6.13.y | Not found

Note: The patch differs from the upstream commit:
---
1: 55c85fa7579dc ! 1: 5c6d205c63555 iommufd: Fail replace if device has not been attached
@@ Commit message

+ (cherry picked from commit 55c85fa7579dc2e3f5399ef5bad67a44257c1a48)
+ Signed-off-by: Yi Liu <[email protected]>

## drivers/iommu/iommufd/device.c ##
@@ drivers/iommu/iommufd/device.c: iommufd_device_attach_reserved_iova(struct iommufd_device *idev,
+ return 0;
+ }

- /* The device attach/detach/replace helpers for attach_handle */
-
++/* The device attach/detach/replace helpers for attach_handle */
++
+/* Check if idev is attached to igroup->hwpt */
+static bool iommufd_device_is_attached(struct iommufd_device *idev)
+{
@@ drivers/iommu/iommufd/device.c: iommufd_device_attach_reserved_iova(struct iommu
+ return false;
+}
+
- static int iommufd_hwpt_attach_device(struct iommufd_hw_pagetable *hwpt,
- struct iommufd_device *idev)
+ int iommufd_hw_pagetable_attach(struct iommufd_hw_pagetable *hwpt,
+ struct iommufd_device *idev)
{
@@ drivers/iommu/iommufd/device.c: iommufd_device_do_replace(struct iommufd_device *idev,
goto err_unlock;
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-6.12.y       |  Success    |  Success   |