FAILED: patch "[PATCH] drm/gpusvm: publish dpagemap early to avoid device mapping" failed to apply to 6.18-stable tree

The patch below does not apply to the 6.18-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-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 7f708f51e3955bda0d77a0b67ab9bea6c97fea99
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026072912-heritage-womb-d38a@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

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

From 7f708f51e3955bda0d77a0b67ab9bea6c97fea99 Mon Sep 17 00:00:00 2001
From: Honglei Huang <[email protected]>
Date: Wed, 1 Jul 2026 14:28:00 +0800
Subject: [PATCH] drm/gpusvm: publish dpagemap early to avoid device mapping
leak on error

drm_gpusvm_get_pages() only stored the local dpagemap into svm_pages->dpagemap on the success path. If a later page failed (e.g. -EOPNOTSUPP when ctx->allow_mixed is false) and jumped to err_unmap, svm_pages->dpagemap was still NULL, so __drm_gpusvm_unmap_pages() skipped device_unmap() and leaked the device mappings already created.

Assign svm_pages->dpagemap when the first device page is mapped so the err_unmap path can device_unmap() those mappings.

This issue was found by Sashiko AI review.

index 44bb19658dd6..9a06ff7d2608 100644
@@ -1544,6 +1544,16 @@ int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,
 					err = -EAGAIN;
 					goto err_unmap;
 				}
+
+				/*
+				 * Set the dpagemap as soon as the first
+				 * device page is mapped so the err_unmap path
+				 * can device_unmap() the device mappings that
+				 * have already been created.
+				 */
+				drm_pagemap_get(dpagemap);
+				drm_pagemap_put(svm_pages->dpagemap);
+				svm_pages->dpagemap = dpagemap;
 			}
 			svm_pages->dma_addr[j] =
 				dpagemap->ops->device_map(dpagemap,

@@ -1611,12 +1621,8 @@ int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,
 			goto err_unmap;
 	}
 
-	if (pagemap) {
+	if (pagemap)
 		flags.has_devmem_pages = true;
-		drm_pagemap_get(dpagemap);
-		drm_pagemap_put(svm_pages->dpagemap);
-		svm_pages->dpagemap = dpagemap;
-	}
 
 	/* WRITE_ONCE pairs with READ_ONCE for opportunistic checks */
 	WRITE_ONCE(svm_pages->flags.__flags, flags.__flags);

drm_gpusvm_get_pages() only stored the local dpagemap into svm_pages->dpagemap on the success path. If a later page failed (e.g. -EOPNOTSUPP when ctx->allow_mixed is false) and jumped to err_unmap, svm_pages->dpagemap was still NULL, so __drm_gpusvm_unmap_pages() skipped device_unmap() and leaked the device mappings already created.

Assign svm_pages->dpagemap when the first device page is mapped so the err_unmap path can device_unmap() those mappings.

This issue was found by Sashiko AI review.

[ Adjusted for 6.18.y: drop drm_pagemap_get()/drm_pagemap_put() around the
svm_pages->dpagemap assignment; that reference counting is not present in 6.18 where the field is not refcounted (unmap path only clears it). ]

---
 drivers/gpu/drm/drm_gpusvm.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

index 4cde5bf4ae..a22beafa01 100644
@@ -1390,6 +1390,14 @@ int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,
 					err = -EAGAIN;
 					goto err_unmap;
 				}
+
+				/*
+				 * Set the dpagemap as soon as the first
+				 * device page is mapped so the err_unmap path
+				 * can device_unmap() the device mappings that
+				 * have already been created.
+				 */
+				svm_pages->dpagemap = dpagemap;
 			}
 			svm_pages->dma_addr[j] =
 				dpagemap->ops->device_map(dpagemap,

@@ -1432,10 +1440,8 @@ int drm_gpusvm_get_pages(struct drm_gpusvm *gpusvm,
 		flags.has_dma_mapping = true;
 	}
 
-	if (pagemap) {
+	if (pagemap)
 		flags.has_devmem_pages = true;
-		svm_pages->dpagemap = dpagemap;
-	}
 
 	/* WRITE_ONCE pairs with READ_ONCE for opportunistic checks */
 	WRITE_ONCE(svm_pages->flags.__flags, flags.__flags);

2.34.1

Queued for 6.18, thanks.

Thanks,
Sasha