From 12f15d52d38ac53f7c70ea3d4b3d76afed04e064 Mon Sep 17 00:00:00 2001 From: Tvrtko Ursulin Date: Fri, 23 Jan 2026 14:15:40 +0000 Subject: [PATCH] drm: Do not allow userspace to trigger kernel warnings in drm_gem_change_handle_ioctl() MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Since GEM bo handles are u32 in the uapi and the internal implementation uses idr_alloc() which uses int ranges, passing a new handle larger than INT_MAX trivially triggers a kernel warning: idr_alloc(): ... if (WARN_ON_ONCE(start < 0)) return -EINVAL; ... Fix it by rejecting new handles above INT_MAX and at the same time make the end limit calculation more obvious by moving into int domain. Signed-off-by: Tvrtko Ursulin Reported-by: Zhi Wang Fixes: 53096728b891 ("drm: Add DRM prime interface to reassign GEM handle") Cc: David Francis Cc: Felix Kuehling Cc: Christian König Cc: # v6.18+ Tested-by: Harshit Mogalapalli Reviewed-by: Christian König Signed-off-by: Tvrtko Ursulin Link: https://lore.kernel.org/r/20260123141540.76540-1-tvrtko.ursulin@igalia.com --- drivers/gpu/drm/drm_gem.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c index e4df43427394..25f68fed9b48 100644 --- a/drivers/gpu/drm/drm_gem.c +++ b/drivers/gpu/drm/drm_gem.c @@ -960,16 +960,21 @@ int drm_gem_change_handle_ioctl(struct drm_device *dev, void *data, { struct drm_gem_change_handle *args = data; struct drm_gem_object *obj; - int ret; + int handle, ret; if (!drm_core_check_feature(dev, DRIVER_GEM)) return -EOPNOTSUPP; + /* idr_alloc() limitation. */ + if (args->new_handle > INT_MAX) + return -EINVAL; + handle = args->new_handle; + obj = drm_gem_object_lookup(file_priv, args->handle); if (!obj) return -ENOENT; - if (args->handle == args->new_handle) { + if (args->handle == handle) { ret = 0; goto out; } @@ -977,18 +982,19 @@ int drm_gem_change_handle_ioctl(struct drm_device *dev, void *data, mutex_lock(&file_priv->prime.lock); spin_lock(&file_priv->table_lock); - ret = idr_alloc(&file_priv->object_idr, obj, - args->new_handle, args->new_handle + 1, GFP_NOWAIT); + ret = idr_alloc(&file_priv->object_idr, obj, handle, handle + 1, + GFP_NOWAIT); spin_unlock(&file_priv->table_lock); if (ret < 0) goto out_unlock; if (obj->dma_buf) { - ret = drm_prime_add_buf_handle(&file_priv->prime, obj->dma_buf, args->new_handle); + ret = drm_prime_add_buf_handle(&file_priv->prime, obj->dma_buf, + handle); if (ret < 0) { spin_lock(&file_priv->table_lock); - idr_remove(&file_priv->object_idr, args->new_handle); + idr_remove(&file_priv->object_idr, handle); spin_unlock(&file_priv->table_lock); goto out_unlock; } -- 2.47.3