drm: add DRM_SET_CLIENT_NAME ioctl

Giving the opportunity to userspace to associate a free-form
name with a drm_file struct is helpful for tracking and debugging.

This is similar to the existing DMA_BUF_SET_NAME ioctl.

Access to client_name is protected by a mutex, and the 'clients' debugfs
file has been updated to print it.

Userspace MR to use this ioctl:
   https://gitlab.freedesktop.org/virgl/virglrenderer/-/merge_requests/1428

If the string passed by userspace contains chars that would mess up output
when it's going to be printed (in dmesg, fdinfo, etc), -EINVAL is returned.

A 0-length string is a valid use, and clears the existing name.

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Reviewed-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241003124506.470931-2-pierre-eric.pelloux-prayer@amd.com
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>

1 files changed, 51 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index 51f39912866f..f593dc569d31 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -540,6 +540,55 @@ int drm_version(struct drm_device *dev, void *data,
 	return err;
 }
 
+/*
+ * Check if the passed string contains control char or spaces or
+ * anything that would mess up a formatted output.
+ */
+static int drm_validate_value_string(const char *value, size_t len)
+{
+	int i;
+
+	for (i = 0; i < len; i++) {
+		if (!isascii(value[i]) || !isgraph(value[i]))
+			return -EINVAL;
+	}
+	return 0;
+}
+
+static int drm_set_client_name(struct drm_device *dev, void *data,
+			       struct drm_file *file_priv)
+{
+	struct drm_set_client_name *name = data;
+	size_t len = name->name_len;
+	void __user *user_ptr;
+	char *new_name;
+
+	if (len > DRM_CLIENT_NAME_MAX_LEN) {
+		return -EINVAL;
+	} else if (len) {
+		user_ptr = u64_to_user_ptr(name->name);
+
+		new_name = memdup_user_nul(user_ptr, len);
+		if (IS_ERR(new_name))
+			return PTR_ERR(new_name);
+
+		if (strlen(new_name) != len ||
+		    drm_validate_value_string(new_name, len) < 0) {
+			kfree(new_name);
+			return -EINVAL;
+		}
+	} else {
+		new_name = NULL;
+	}
+
+	mutex_lock(&file_priv->client_name_lock);
+	kfree(file_priv->client_name);
+	file_priv->client_name = new_name;
+	mutex_unlock(&file_priv->client_name_lock);
+
+	return 0;
+}
+
 static int drm_ioctl_permit(u32 flags, struct drm_file *file_priv)
 {
 	/* ROOT_ONLY is only for CAP_SYS_ADMIN */
@@ -610,6 +659,8 @@ static const struct drm_ioctl_desc drm_ioctls[] = {
 	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_SET_CLIENT_NAME, drm_set_client_name, 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),
 	DRM_IOCTL_DEF(DRM_IOCTL_MODE_SETCRTC, drm_mode_setcrtc, DRM_MASTER),