[PATCH 6.18 006/396] drm/gpusvm: publish dpagemap early to avoid device mapping leak on error

6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Honglei Huang <[email protected]>

commit 7f708f51e3955bda0d77a0b67ab9bea6c97fea99 upstream.

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.

Fixes: f70da6f99d4f ("drm/gpusvm: pull out drm_gpusvm_pages substructure")
Cc: [email protected]
Reviewed-by: Matthew Brost <[email protected]>
Signed-off-by: Honglei Huang <[email protected]>
Signed-off-by: Matthew Brost <[email protected]>
Link: https://patch.msgid.link/[email protected]
[ 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). ]
Signed-off-by: Honglei Huang <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
---
 drivers/gpu/drm/drm_gpusvm.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/drm_gpusvm.c b/drivers/gpu/drm/drm_gpusvm.c
index 781cd4e5b704..e5c7befe3108 100644
--- a/drivers/gpu/drm/drm_gpusvm.c
+++ b/drivers/gpu/drm/drm_gpusvm.c
@@ -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);
-- 
2.53.0