[PATCH v2] drm: drop DRM_AUTH from PRIME_TO/FROM_HANDLE ioctls

[Emil Velikov]

From: Emil Velikov <emil.veli...@collabora.com>

Current validation requires that we're authenticated, even though we can
bypass (by design) the authentication when using a render node.

Let's address the former by following the design decision.

v2: Add simpler validation in the ioctls themselves (Boris)

Cc: Alex Deucher <alexander.deuc...@amd.com>
Cc: amd-gfx@lists.freedesktop.org
Cc: Boris Brezillon <boris.brezil...@collabora.com>
Cc: Daniel Vetter <dan...@ffwll.ch>
Cc: Sean Paul <s...@poorly.run>
Acked-by: Christian König <christian.koe...@amd.com>
Signed-off-by: Emil Velikov <emil.veli...@collabora.com>
---
 drivers/gpu/drm/drm_ioctl.c |  4 ++--
 drivers/gpu/drm/drm_prime.c | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index fcd728d7cf72..5afb39688b55 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -652,8 +652,8 @@ static const struct drm_ioctl_desc drm_ioctls[] = {
 
        DRM_IOCTL_DEF(DRM_IOCTL_MODE_GETRESOURCES, drm_mode_getresources, 0),
 
-       DRM_IOCTL_DEF(DRM_IOCTL_PRIME_HANDLE_TO_FD, 
drm_prime_handle_to_fd_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
-       DRM_IOCTL_DEF(DRM_IOCTL_PRIME_FD_TO_HANDLE, 
drm_prime_fd_to_handle_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),
+       DRM_IOCTL_DEF(DRM_IOCTL_PRIME_HANDLE_TO_FD, 
drm_prime_handle_to_fd_ioctl, DRM_RENDER_ALLOW),
+       DRM_IOCTL_DEF(DRM_IOCTL_PRIME_FD_TO_HANDLE, 
drm_prime_fd_to_handle_ioctl, DRM_RENDER_ALLOW),
 
        DRM_IOCTL_DEF(DRM_IOCTL_MODE_GETPLANERESOURCES, drm_mode_getplane_res, 
0),
        DRM_IOCTL_DEF(DRM_IOCTL_MODE_GETCRTC, drm_mode_getcrtc, 0),
diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 0a2316e0e812..dab166c860ec 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -358,11 +358,27 @@ int drm_gem_prime_fd_to_handle(struct drm_device *dev,
 }
 EXPORT_SYMBOL(drm_gem_prime_fd_to_handle);
 
+static inline bool
+allowed_ioctl(struct drm_device *dev, struct drm_file *file_priv)
+{
+       /* Unauthenticated master is allowed, for render capable devices */
+       if (drm_is_primary_client(file_priv)) {
+               if (!file_priv->authenticated &&
+                   !drm_core_check_feature(dev, DRIVER_RENDER))
+               return false;
+       }
+
+       return true;
+}
+
 int drm_prime_fd_to_handle_ioctl(struct drm_device *dev, void *data,
                                 struct drm_file *file_priv)
 {
        struct drm_prime_handle *args = data;
 
+       if (!allowed_ioctl(dev, file_priv))
+               return -EACCES;
+
        if (!dev->driver->prime_fd_to_handle)
                return -ENOSYS;
 
@@ -511,6 +527,9 @@ int drm_prime_handle_to_fd_ioctl(struct drm_device *dev, 
void *data,
 {
        struct drm_prime_handle *args = data;
 
+       if (!allowed_ioctl(dev, file_priv))
+               return -EACCES;
+
        if (!dev->driver->prime_handle_to_fd)
                return -ENOSYS;
 
-- 
2.23.0

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