[PATCH 6.19.y 6.18.y 0/2] drm/exynos: vidi: fix various memory corruption bugs

[PATCH 6.19.y 6.18.y 0/2] drm/exynos: vidi: fix various memory corruption bugs

[Jeongjun Park]

This backport patch should have been backported along with commit 52b330799e2d
("drm/exynos: vidi: use ctx->lock to protect struct vidi_context member
variables related to memory alloc/free"), but was written separately because
some commits were missing.

https://lore.kernel.org/all/20260119082553.195181-1-aha310510@gmail.com/

After this patch is backported, we plan to write additional patches to
backport to the remaining longterm kernels.

Jeongjun Park (2):
  drm/exynos: vidi: use priv->vidi_dev for ctx lookup in vidi_connection_ioctl()
  drm/exynos: vidi: fix to avoid directly dereferencing user pointer

 drivers/gpu/drm/exynos/exynos_drm_drv.h  |  1 +
 drivers/gpu/drm/exynos/exynos_drm_vidi.c | 36 +++++++++++++++++++++++++++++++-----
 2 files changed, 32 insertions(+), 5 deletions(-)

[PATCH 6.19.y 6.18.y 1/2] drm/exynos: vidi: use priv->vidi_dev for ctx lookup in vidi_connection_ioctl()

[Jeongjun Park]

[ Upstream commit d3968a0d85b211e197f2f4f06268a7031079e0d0 ]

vidi_connection_ioctl() retrieves the driver_data from drm_dev->dev to
obtain a struct vidi_context pointer. However, drm_dev->dev is the
exynos-drm master device, and the driver_data contained therein is not
the vidi component device, but a completely different device.

This can lead to various bugs, ranging from null pointer dereferences and
garbage value accesses to, in unlucky cases, out-of-bounds errors,
use-after-free errors, and more.

To resolve this issue, we need to store/delete the vidi device pointer in
exynos_drm_private->vidi_dev during bind/unbind, and then read this
exynos_drm_private->vidi_dev within ioctl() to obtain the correct
struct vidi_context pointer.

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_drv.h  |  1 +
 drivers/gpu/drm/exynos/exynos_drm_vidi.c | 14 +++++++++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/exynos/exynos_drm_drv.h b/drivers/gpu/drm/exynos/exynos_drm_drv.h
index 23646e55f142..06c29ff2aac0 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_drv.h
+++ b/drivers/gpu/drm/exynos/exynos_drm_drv.h
@@ -199,6 +199,7 @@ struct drm_exynos_file_private {
 struct exynos_drm_private {
 	struct device *g2d_dev;
 	struct device *dma_dev;
+	struct device *vidi_dev;
 	void *mapping;
 
 	/* for atomic commit */
diff --git a/drivers/gpu/drm/exynos/exynos_drm_vidi.c b/drivers/gpu/drm/exynos/exynos_drm_vidi.c
index e094b8bbc0f1..1fe297d512e7 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_vidi.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_vidi.c
@@ -223,9 +223,14 @@ ATTRIBUTE_GROUPS(vidi);
 int vidi_connection_ioctl(struct drm_device *drm_dev, void *data,
 				struct drm_file *file_priv)
 {
-	struct vidi_context *ctx = dev_get_drvdata(drm_dev->dev);
+	struct exynos_drm_private *priv = drm_dev->dev_private;
+	struct device *dev = priv ? priv->vidi_dev : NULL;
+	struct vidi_context *ctx = dev ? dev_get_drvdata(dev) : NULL;
 	struct drm_exynos_vidi_connection *vidi = data;
 
+	if (!ctx)
+		return -ENODEV;
+
 	if (!vidi) {
 		DRM_DEV_DEBUG_KMS(ctx->dev,
 				  "user data for vidi is null.\n");
@@ -371,6 +376,7 @@ static int vidi_bind(struct device *dev, struct device *master, void *data)
 {
 	struct vidi_context *ctx = dev_get_drvdata(dev);
 	struct drm_device *drm_dev = data;
+	struct exynos_drm_private *priv = drm_dev->dev_private;
 	struct drm_encoder *encoder = &ctx->encoder;
 	struct exynos_drm_plane *exynos_plane;
 	struct exynos_drm_plane_config plane_config = { 0 };
@@ -378,6 +384,8 @@ static int vidi_bind(struct device *dev, struct device *master, void *data)
 	int ret;
 
 	ctx->drm_dev = drm_dev;
+	if (priv)
+		priv->vidi_dev = dev;
 
 	plane_config.pixel_formats = formats;
 	plane_config.num_pixel_formats = ARRAY_SIZE(formats);
@@ -423,8 +431,12 @@ static int vidi_bind(struct device *dev, struct device *master, void *data)
 static void vidi_unbind(struct device *dev, struct device *master, void *data)
 {
 	struct vidi_context *ctx = dev_get_drvdata(dev);
+	struct drm_device *drm_dev = data;
+	struct exynos_drm_private *priv = drm_dev->dev_private;
 
 	timer_delete_sync(&ctx->timer);
+	if (priv)
+		priv->vidi_dev = NULL;
 }
 
 static const struct component_ops vidi_component_ops = {
--

[PATCH 6.19.y 6.18.y 2/2] drm/exynos: vidi: fix to avoid directly dereferencing user pointer

[Jeongjun Park]

[ 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 | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/exynos/exynos_drm_vidi.c b/drivers/gpu/drm/exynos/exynos_drm_vidi.c
index 1fe297d512e7..601406b640c7 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_vidi.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_vidi.c
@@ -251,13 +251,27 @@ int vidi_connection_ioctl(struct drm_device *drm_dev, void *data,
 
 	if (vidi->connection) {
 		const struct drm_edid *drm_edid;
-		const struct edid *raw_edid;
+		const void __user *edid_userptr = u64_to_user_ptr(vidi->edid);
+		void *edid_buf;
+		struct edid hdr;
 		size_t size;
 
-		raw_edid = (const struct edid *)(unsigned long)vidi->edid;
-		size = (raw_edid->extensions + 1) * EDID_LENGTH;
+		if (copy_from_user(&hdr, edid_userptr, sizeof(hdr)))
+			return -EFAULT;
 
-		drm_edid = drm_edid_alloc(raw_edid, size);
+		size = (hdr.extensions + 1) * EDID_LENGTH;
+
+		edid_buf = kmalloc(size, GFP_KERNEL);
+		if (!edid_buf)
+			return -ENOMEM;
+
+		if (copy_from_user(edid_buf, edid_userptr, size)) {
+			kfree(edid_buf);
+			return -EFAULT;
+		}
+
+		drm_edid = drm_edid_alloc(edid_buf, size);
+		kfree(edid_buf);
 		if (!drm_edid)
 			return -ENOMEM;
 
--