FAILED: patch "[PATCH] xen/gntdev: Fix gntdev_dmabuf ref leak in dmabuf_exp_wait_released()" failed to apply to 6.18-stable tree

[Sasha Levin <sashal@kernel.org>]

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 <stable@vger.kernel.org>.

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 6f165abe2b40ede71c98956cd74cd17c18505e75
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261107050950-failed-6.18-6f165abe2b40@kernel.org' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Thanks,
Sasha

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

From 6f165abe2b40ede71c98956cd74cd17c18505e75 Mon Sep 17 00:00:00 2001
From: Wentao Liang <vulab@iscas.ac.cn>
Date: Wed, 16 Sep 2026 17:09:56 +0000
Subject: [PATCH] xen/gntdev: Fix gntdev_dmabuf ref leak in
 dmabuf_exp_wait_released()

dmabuf_exp_wait_released() takes a reference on the exported
gntdev_dmabuf with dmabuf_exp_wait_obj_get_dmabuf() and passes it to
dmabuf_exp_wait_obj_new(), which drops that reference after adding the
wait object to the wait list.  When the wait object allocation fails,
dmabuf_exp_wait_obj_new() returns ERR_PTR(-ENOMEM) early and the
reference is never dropped, leaking a reference to the exported
gntdev_dmabuf.

Drop the reference on the allocation failure path so the reference is
consumed whether the wait object is created or not.

Fixes: 932d6562179e ("xen/gntdev: Add initial support for dma-buf UAPI")
Cc: stable@vger.kernel.org
Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-ID: <20260916170956.2086505-1-vulab@iscas.ac.cn>
---
 drivers/xen/gntdev-dmabuf.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/gntdev-dmabuf.c b/drivers/xen/gntdev-dmabuf.c
index 83b0df4608941..df1883aca850e 100644
--- a/drivers/xen/gntdev-dmabuf.c
+++ b/drivers/xen/gntdev-dmabuf.c
@@ -96,8 +96,10 @@ dmabuf_exp_wait_obj_new(struct gntdev_dmabuf_priv *priv,
 	struct gntdev_dmabuf_wait_obj *obj;
 
 	obj = kzalloc_obj(*obj);
-	if (!obj)
+	if (!obj) {
+		kref_put(&gntdev_dmabuf->u.exp.refcount, dmabuf_exp_release);
 		return ERR_PTR(-ENOMEM);
+	}
 
 	init_completion(&obj->completion);
 	obj->gntdev_dmabuf = gntdev_dmabuf;
-- 
2.53.0