drm/exynos: vidi: fix to avoid directly dereferencing user pointer

commit d4c98c077c7fb2dfdece7d605e694b5ea2665085 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/exynos/exynos_drm_vidi.c b/drivers/gpu/drm/exynos/exynos_drm_vidi.c
index 02e22806450577248d850463277ac80822bee3c7..67bbf9b8bc0ef84f7152de6cf3bd3e7601f391ef 100644 (file)
--- a/drivers/gpu/drm/exynos/exynos_drm_vidi.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_vidi.c
@@ -263,13 +263,27 @@ 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;