From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8C4FFC5B572 for ; Fri, 14 Aug 2026 21:08:42 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 15CE410F73C; Fri, 14 Aug 2026 21:08:42 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="mtTGAkW5"; dkim-atps=neutral Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by gabe.freedesktop.org (Postfix) with ESMTPS id AC26610F73C; Fri, 14 Aug 2026 21:08:40 +0000 (UTC) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 6266740292; Fri, 14 Aug 2026 21:08:40 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AC6AF1F000E9; Fri, 14 Aug 2026 21:08:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786741720; bh=rMcM0lBlPoPh1FiorELQJDBDv6Kiof5qqVa1jsW625k=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=mtTGAkW50fZxxenfAzuyu0UFNDw/J7doURQ0Dhd69su0npvC2IZfOSmYnBXGgduBj uIFl07kEDemyqgFsMBYLtsmyW5VWVxcWj7S7uNo99a7LIHSqsSxtoiTotSuscuYfRr ETiTqR6xt2MGNSSod9Cyijd1FS6mIMY/kyHbgNxQIXDsJ4G7AqnVwGCT57fV96XrQf /mdaz6NwfF/9/pYWV+BZYPVmbBQgUtFhfz02eSLoAyqm+pOniop5tNQ44ZU2PvwZ87 r0sieZCZBgD87zLv6yjNgKRjwon6SBH9rxwCKE/y0UFm+dVlRvNS+pOkitiqDclJPC wQr5iu3OlO7FA== From: sashiko-bot@kernel.org Subject: Re: [PATCH 5/5] drm/vblank: Require all CRTCs implement vblank support in drm_vblank_init() To: "Lyude Paul" Cc: linux-sunxi@lists.linux.dev, Frank.Li@kernel.org, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, linux-hyperv@vger.kernel.org, neil.armstrong@linaro.org, linux-amlogic@lists.infradead.org, wsa+renesas@sang-engineering.com, intel-xe@lists.freedesktop.org, imx@lists.linux.dev In-Reply-To: <20260814203542.1405135-6-lyude@redhat.com> References: <20260814203542.1405135-1-lyude@redhat.com> <20260814203542.1405135-6-lyude@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Fri, 14 Aug 2026 21:08:39 +0000 Message-Id: <20260814210839.AC6AF1F000E9@smtp.kernel.org> X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: sashiko-reviews@lists.linux.dev Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Thank you for your contribution! Sashiko AI review found 1 potential issue(= s) to consider: - [High] drm_vblank_init() causes a NULL pointer dereference or driver prob= e failure due to accessing uninitialized or empty crtc_list -- --- Patch [5]: [PATCH 5/5] drm/vblank: Require all CRTCs implement vblank s= upport in drm_vblank_init() --- commit 178bbb448a16663eaad60425c62b446801e0f387 Author: Lyude Paul drm/vblank: Require all CRTCs implement vblank support in drm_vblank_init() This commit modifies drm_vblank_init() to verify that all CRTCs implement vblank support, ensuring an all-or-nothing configuration. It returns -EINVAL if support is mixed, and -ENODEV if no CRTCs support vblank. > diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c > index d57405050554f..17affae23e7a6 100644 > --- a/drivers/gpu/drm/drm_vblank.c > +++ b/drivers/gpu/drm/drm_vblank.c > @@ -542,12 +542,31 @@ static void drm_vblank_init_release(struct drm_devi= ce *dev, void *ptr) > * drmm_add_action_or_reset(). > * > * Returns: > - * Zero on success or a negative error code on failure. > + * Zero on success or a negative error code on failure. If no CRTCs with= vblank > + * support implemented were found, -ENODEV will be returned. > */ > int drm_vblank_init(struct drm_device *dev) > { > int ret; > struct drm_crtc *crtc; > + bool found_vbl_crtc =3D false, found_non_vbl_crtc =3D false; > + > + /* Vblank hooks are per-CRTC, not per-device - which is contrary to how > + * the vblank core was written. Since hardware that only has vblank > + * support on some CRTCs but not all is non-existent and would likely > + * lead to UB, ensure that vblank support is all or nothing. > + */ > + drm_for_each_crtc(crtc, dev) { [Severity: High] Can iterating over dev->mode_config.crtc_list here cause a NULL pointer dereference or a false -ENODEV return during driver probe? Several DRM drivers call drm_vblank_init() before initializing mode_config or creating CRTCs. For example: In i915, intel_display_driver_probe_noirq() calls drm_vblank_init() before intel_mode_config_init() sets up the crtc_list, meaning the list head is uninitialized. In vkms, vkms_create() calls drm_vblank_init() before vkms_modeset_init() initializes the crtc_list. In zynqmp_kms, zynqmp_dpsub_drm_init() initializes the list but calls drm_vblank_init() before any CRTCs are created, meaning the list is empty and this function will unconditionally return -ENODEV. Does drm_vblank_init() need to support being called before CRTCs are registered? > + if (crtc->funcs->enable_vblank) > + found_vbl_crtc =3D true; > + else > + found_non_vbl_crtc =3D true; > + > + if (drm_WARN_ON(dev, found_vbl_crtc && found_non_vbl_crtc)) > + return -EINVAL; > + } > + if (!found_vbl_crtc) > + return -ENODEV; --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20260814203542.1405= 135-1-lyude@redhat.com?part=3D5