[PATCH 6.6.y 0/3] drm/exynos: vidi: fix various memory corruption bugs

[PATCH 6.6.y 0/3] drm/exynos: vidi: fix various memory corruption bugs

[Jeongjun Park]

This backport patch is for 6.6.y only and fixes a bug in the
Exynos VIDI driver.

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

Jeongjun Park (3):
  drm/exynos: vidi: use priv->vidi_dev for ctx lookup in vidi_connection_ioctl()
  drm/exynos: vidi: fix to avoid directly dereferencing user pointer
  drm/exynos: vidi: use ctx->lock to protect struct vidi_context member variables related to memory alloc/free

 drivers/gpu/drm/exynos/exynos_drm_drv.h  |  1 +
 drivers/gpu/drm/exynos/exynos_drm_vidi.c | 72 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-------------
 2 files changed, 60 insertions(+), 13 deletions(-)

[PATCH 6.6.y 1/3] 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 6de0cced6c9d..b31eefb3a8b1 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");
@@ -374,6 +379,7 @@ 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 };
@@ -381,6 +387,8 @@ 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);
@@ -426,8 +434,12 @@ 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;
 
 	del_timer_sync(&ctx->timer);
+	if (priv)
+		priv->vidi_dev = NULL;
 }
 
 static const struct component_ops vidi_component_ops = {
--

[PATCH 6.6.y 2/3] 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 | 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
--

[PATCH 6.6.y 3/3] drm/exynos: vidi: use ctx->lock to protect struct vidi_context member variables related to memory alloc/free

[Jeongjun Park]

[ Upstream commit 52b330799e2d6f825ae2bb74662ec1b10eb954bb ]

Exynos Virtual Display driver performs memory alloc/free operations
without lock protection, which easily causes concurrency problem.

For example, use-after-free can occur in race scenario like this:
```
	CPU0				CPU1				CPU2
	----				----				----
  vidi_connection_ioctl()
    if (vidi->connection) // true
      drm_edid = drm_edid_alloc(); // alloc drm_edid
      ...
      ctx->raw_edid = drm_edid;
      ...
								drm_mode_getconnector()
								  drm_helper_probe_single_connector_modes()
								    vidi_get_modes()
								      if (ctx->raw_edid) // true
								        drm_edid_dup(ctx->raw_edid);
								          if (!drm_edid) // false
								          ...
				vidi_connection_ioctl()
				  if (vidi->connection) // false
				    drm_edid_free(ctx->raw_edid); // free drm_edid
				    ...
								          drm_edid_alloc(drm_edid->edid)
								            kmemdup(edid); // UAF!!
								            ...
```

To prevent these vulns, at least in vidi_context, member variables related
to memory alloc/free should be protected with ctx->lock.

Cc: <stable@vger.kernel.org>
Signed-off-by: Jeongjun Park <aha310510@gmail.com>
---
 drivers/gpu/drm/exynos/exynos_drm_vidi.c | 43 +++++++++++++++++++-----
 1 file changed, 35 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/exynos/exynos_drm_vidi.c b/drivers/gpu/drm/exynos/exynos_drm_vidi.c
index 576d79ebe9a8..b7eae2469b31 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_vidi.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_vidi.c
@@ -186,15 +186,17 @@ static ssize_t vidi_store_connection(struct device *dev,
 				const char *buf, size_t len)
 {
 	struct vidi_context *ctx = dev_get_drvdata(dev);
-	int ret;
+	int ret, new_connected;
 
-	ret = kstrtoint(buf, 0, &ctx->connected);
+	ret = kstrtoint(buf, 0, &new_connected);
 	if (ret)
 		return ret;
 
-	if (ctx->connected > 1)
+	if (new_connected > 1)
 		return -EINVAL;
 
+	mutex_lock(&ctx->lock);
+
 	/* use fake edid data for test. */
 	if (!ctx->raw_edid)
 		ctx->raw_edid = (struct edid *)fake_edid_info;
@@ -202,14 +204,21 @@ static ssize_t vidi_store_connection(struct device *dev,
 	/* if raw_edid isn't same as fake data then it can't be tested. */
 	if (ctx->raw_edid != (struct edid *)fake_edid_info) {
 		DRM_DEV_DEBUG_KMS(dev, "edid data is not fake data.\n");
-		return -EINVAL;
+		ret = -EINVAL;
+		goto fail;
 	}
 
+	ctx->connected = new_connected;
+	mutex_unlock(&ctx->lock);
+
 	DRM_DEV_DEBUG_KMS(dev, "requested connection.\n");
 
 	drm_helper_hpd_irq_event(ctx->drm_dev);
 
 	return len;
+fail:
+	mutex_unlock(&ctx->lock);
+	return ret;
 }
 
 static DEVICE_ATTR(connection, 0644, vidi_show_connection,
@@ -244,11 +253,14 @@ int vidi_connection_ioctl(struct drm_device *drm_dev, void *data,
 		return -EINVAL;
 	}
 
+	mutex_lock(&ctx->lock);
 	if (ctx->connected == vidi->connection) {
+		mutex_unlock(&ctx->lock);
 		DRM_DEV_DEBUG_KMS(ctx->dev,
 				  "same connection request.\n");
 		return -EINVAL;
 	}
+	mutex_unlock(&ctx->lock);
 
 	if (vidi->connection) {
 		struct edid *raw_edid;
@@ -271,20 +283,27 @@ int vidi_connection_ioctl(struct drm_device *drm_dev, void *data,
 					  "failed to allocate raw_edid.\n");
 			return -ENOMEM;
 		}
+		mutex_lock(&ctx->lock);
 		ctx->raw_edid = raw_edid;
+		mutex_unlock(&ctx->lock);
 	} else {
 		/*
 		 * with connection = 0, free raw_edid
 		 * only if raw edid data isn't same as fake data.
 		 */
+		mutex_lock(&ctx->lock);
 		if (ctx->raw_edid && ctx->raw_edid !=
 				(struct edid *)fake_edid_info) {
 			kfree(ctx->raw_edid);
 			ctx->raw_edid = NULL;
 		}
+		mutex_unlock(&ctx->lock);
 	}
 
+	mutex_lock(&ctx->lock);
 	ctx->connected = vidi->connection;
+	mutex_unlock(&ctx->lock);
+
 	drm_helper_hpd_irq_event(ctx->drm_dev);
 
 	return 0;
@@ -299,7 +318,7 @@ static enum drm_connector_status vidi_detect(struct drm_connector *connector,
 	 * connection request would come from user side
 	 * to do hotplug through specific ioctl.
 	 */
-	return ctx->connected ? connector_status_connected :
+	return READ_ONCE(ctx->connected) ? connector_status_connected :
 			connector_status_disconnected;
 }
 
@@ -321,22 +340,24 @@ static int vidi_get_modes(struct drm_connector *connector)
 	struct vidi_context *ctx = ctx_from_connector(connector);
 	struct edid *edid;
 	int edid_len;
-	int count;
+	int count = 0;
 
 	/*
 	 * the edid data comes from user side and it would be set
 	 * to ctx->raw_edid through specific ioctl.
 	 */
+
+	mutex_lock(&ctx->lock);
 	if (!ctx->raw_edid) {
 		DRM_DEV_DEBUG_KMS(ctx->dev, "raw_edid is null.\n");
-		return 0;
+		goto fail;
 	}
 
 	edid_len = (1 + ctx->raw_edid->extensions) * EDID_LENGTH;
 	edid = kmemdup(ctx->raw_edid, edid_len, GFP_KERNEL);
 	if (!edid) {
 		DRM_DEV_DEBUG_KMS(ctx->dev, "failed to allocate edid\n");
-		return 0;
+		goto fail;
 	}
 
 	drm_connector_update_edid_property(connector, edid);
@@ -345,6 +366,8 @@ static int vidi_get_modes(struct drm_connector *connector)
 
 	kfree(edid);
 
+fail:
+	mutex_unlock(&ctx->lock);
 	return count;
 }
 
@@ -490,11 +513,15 @@ static int vidi_remove(struct platform_device *pdev)
 {
 	struct vidi_context *ctx = platform_get_drvdata(pdev);
 
+	mutex_lock(&ctx->lock);
+
 	if (ctx->raw_edid != (struct edid *)fake_edid_info) {
 		kfree(ctx->raw_edid);
 		ctx->raw_edid = NULL;
 	}
 
+	mutex_unlock(&ctx->lock);
+
 	component_del(&pdev->dev, &vidi_component_ops);
 
 	return 0;
--