From ee9adb7a45516cfa536ca92253d7ae59d56db9e4 Mon Sep 17 00:00:00 2001
From: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Date: Mon, 9 Jan 2023 00:13:11 +0300
Subject: [PATCH] drm/shmem-helper: Remove another errant put in error path
Git-commit: ee9adb7a45516cfa536ca92253d7ae59d56db9e4
Patch-mainline: v6.3-rc3
References: git-fixes

drm_gem_shmem_mmap() doesn't own reference in error code path, resulting
in the dma-buf shmem GEM object getting prematurely freed leading to a
later use-after-free.

Fixes: f49a51bfdc8e ("drm/shme-helpers: Fix dma_buf_mmap forwarding bug")
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230108211311.3950107-1-dmitry.osipenko@collabora.com
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/drm_gem_shmem_helper.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -606,11 +606,14 @@ int drm_gem_shmem_mmap(struct drm_gem_ob
 	int ret;
 
 	if (obj->import_attach) {
-		/* Drop the reference drm_gem_mmap_obj() acquired.*/
-		drm_gem_object_put(obj);
 		vma->vm_private_data = NULL;
+		ret = dma_buf_mmap(obj->dma_buf, vma, 0);
+
+		/* Drop the reference drm_gem_mmap_obj() acquired.*/
+		if (!ret)
+			drm_gem_object_put(obj);
 
-		return dma_buf_mmap(obj->dma_buf, vma, 0);
+		return ret;
 	}
 
 	shmem = to_drm_gem_shmem_obj(obj);