FAILED: patch "[PATCH] drm/vmwgfx: drop dma_buf reference on foreign-fd prime import" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x f739416dc555fa205a785e5135d73fa39b26f35d
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026080533-unsettled-body-61f9@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From f739416dc555fa205a785e5135d73fa39b26f35d Mon Sep 17 00:00:00 2001
From: Zack Rusin <[email protected]>
Date: Tue, 5 May 2026 18:22:26 -0400
Subject: [PATCH] drm/vmwgfx: drop dma_buf reference on foreign-fd prime import

ttm_prime_fd_to_handle() returns -ENOSYS when the imported fd's
dma_buf->ops do not match the ttm_object_device's ops, but does so
without releasing the reference acquired by dma_buf_get().  Any
unprivileged renderD client passing a non-vmwgfx prime fd through the
DRM_VMW_GB_SURFACE_REF{,_EXT} path leaks one dma_buf reference per
call and indefinitely pins the foreign exporter's GEM resources.

Funnel the error path through the existing dma_buf_put() so the
reference is always dropped.

Fixes: 65981f7681ab ("drm/ttm: Add a minimal prime implementation for ttm base objects")
Cc: [email protected]
Assisted-by: Claude:claude-opus-4.7
Signed-off-by: Zack Rusin <[email protected]>
Reviewed-by: Ian Forbes <[email protected]>
Link: https://patch.msgid.link/[email protected]

diff --git a/drivers/gpu/drm/vmwgfx/ttm_object.c b/drivers/gpu/drm/vmwgfx/ttm_object.c
index 2421b0dd057c..f9042bafdc93 100644
--- a/drivers/gpu/drm/vmwgfx/ttm_object.c
+++ b/drivers/gpu/drm/vmwgfx/ttm_object.c
@@ -547,14 +547,17 @@ int ttm_prime_fd_to_handle(struct ttm_object_file *tfile,
 	if (IS_ERR(dma_buf))
 		return PTR_ERR(dma_buf);
 
-	if (dma_buf->ops != &tdev->ops)
-		return -ENOSYS;
+	if (dma_buf->ops != &tdev->ops) {
+		ret = -ENOSYS;
+		goto out;
+	}
 
 	prime = (struct ttm_prime_object *) dma_buf->priv;
 	base = &prime->base;
 	*handle = base->handle;
 	ret = ttm_ref_object_add(tfile, base, NULL, false);
 
+out:
 	dma_buf_put(dma_buf);
 
 	return ret;