[PATCH 6.1.y 5.15.y 5.10.y 2/3] drm/exynos: vidi: fix to avoid directly dereferencing user pointer

[Jeongjun Park <aha310510@gmail.com>]

[ Upstream commit d4c98c077c7fb2dfdece7d605e694b5ea2665085 ]

In vidi_connection_ioctl(), vidi->edid(user pointer) is directly
dereferenced in the kernel.

This allows arbitrary kernel memory access from the user space, so instead
of directly accessing the user pointer in the kernel, we should modify it
to copy edid to kernel memory using copy_from_user() and use it.

Cc: <stable@vger.kernel.org>
Signed-off-by: Jeongjun Park <aha310510@gmail.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
---
 drivers/gpu/drm/exynos/exynos_drm_vidi.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/exynos/exynos_drm_vidi.c b/drivers/gpu/drm/exynos/exynos_drm_vidi.c
index d0e394397eca..576d79ebe9a8 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_vidi.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_vidi.c
@@ -252,19 +252,26 @@ int vidi_connection_ioctl(struct drm_device *drm_dev, void *data,
 
 	if (vidi->connection) {
 		struct edid *raw_edid;
+		struct edid edid_buf;
+		void *edid_userptr = u64_to_user_ptr(vidi->edid);
 
-		raw_edid = (struct edid *)(unsigned long)vidi->edid;
-		if (!drm_edid_is_valid(raw_edid)) {
+		if (copy_from_user(&edid_buf, edid_userptr, sizeof(struct edid)))
+			return -EFAULT;
+
+		if (!drm_edid_is_valid(&edid_buf)) {
 			DRM_DEV_DEBUG_KMS(ctx->dev,
 					  "edid data is invalid.\n");
 			return -EINVAL;
 		}
-		ctx->raw_edid = drm_edid_duplicate(raw_edid);
-		if (!ctx->raw_edid) {
+
+		raw_edid = drm_edid_duplicate(&edid_buf);
+
+		if (!raw_edid) {
 			DRM_DEV_DEBUG_KMS(ctx->dev,
 					  "failed to allocate raw_edid.\n");
 			return -ENOMEM;
 		}
+		ctx->raw_edid = raw_edid;
 	} else {
 		/*
 		 * with connection = 0, free raw_edid
--