From 2e3649e237237258a08d75afef96648dd2b379f7 Mon Sep 17 00:00:00 2001 From: Julian Orth Date: Sun, 1 Mar 2026 13:34:42 +0100 Subject: [PATCH] drm/syncobj: Fix handle <-> fd ioctls with dirty stack MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Consider the following application: #include #include #include #include int main(void) { int fd = open("/dev/dri/renderD128", O_RDWR); struct drm_syncobj_create arg1; ioctl(fd, DRM_IOCTL_SYNCOBJ_CREATE, &arg1); struct drm_syncobj_handle arg2; memset(&arg2, 1, sizeof(arg2)); // simulate dirty stack arg2.handle = arg1.handle; arg2.flags = 0; arg2.fd = 0; arg2.pad = 0; // arg2.point = 0; // userspace is required to set point to 0 ioctl(fd, DRM_IOCTL_SYNCOBJ_HANDLE_TO_FD, &arg2); } The last ioctl returns EINVAL because args->point is not 0. However, userspace developed against older kernel versions is not aware of the new point field and might therefore not initialize it. The correct check would be if (args->flags & DRM_SYNCOBJ_FD_TO_HANDLE_FLAGS_TIMELINE) return -EINVAL; However, there might already be userspace that relies on this not returning an error as long as point == 0. Therefore use the more lenient check. Fixes: c2d3a7300695 ("drm/syncobj: Extend EXPORT_SYNC_FILE for timeline syncobjs") Signed-off-by: Julian Orth Reviewed-by: Christian König Signed-off-by: Christian König Link: https://lore.kernel.org/r/20260301-point-v1-1-21fc5fd98614@gmail.com --- drivers/gpu/drm/drm_syncobj.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c index 250734dee928..49eccb43ce63 100644 --- a/drivers/gpu/drm/drm_syncobj.c +++ b/drivers/gpu/drm/drm_syncobj.c @@ -875,7 +875,7 @@ drm_syncobj_handle_to_fd_ioctl(struct drm_device *dev, void *data, return drm_syncobj_export_sync_file(file_private, args->handle, point, &args->fd); - if (args->point) + if (point) return -EINVAL; return drm_syncobj_handle_to_fd(file_private, args->handle, @@ -909,7 +909,7 @@ drm_syncobj_fd_to_handle_ioctl(struct drm_device *dev, void *data, args->handle, point); - if (args->point) + if (point) return -EINVAL; return drm_syncobj_fd_to_handle(file_private, args->fd,