From nobody Sun Feb 8 15:42:52 2026 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6376AEB64DC for ; Fri, 21 Jul 2023 10:24:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231771AbjGUKYK (ORCPT ); Fri, 21 Jul 2023 06:24:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59628 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232408AbjGUKXs (ORCPT ); Fri, 21 Jul 2023 06:23:48 -0400 Received: from mail.ispras.ru (mail.ispras.ru [83.149.199.84]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8DF591722 for ; Fri, 21 Jul 2023 03:23:44 -0700 (PDT) Received: from localhost.ispras.ru (unknown [10.10.165.9]) by mail.ispras.ru (Postfix) with ESMTPSA id 1128940AE010; Fri, 21 Jul 2023 10:16:45 +0000 (UTC) DKIM-Filter: OpenDKIM Filter v2.11.0 mail.ispras.ru 1128940AE010 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ispras.ru; s=default; t=1689934605; bh=PHPNcQA/mlieAatBPZHyKEUg1u7Tlcm1+az9zlQDbY8=; h=From:To:Cc:Subject:Date:From; b=Z3wdixjAMd9W826oQ5ZAmSGo/4lDkslYNWkikcAg4mZdLItvN5NLoUWTxiBZFfvy1 nhb/vpNqWUKZAAgrz+3p0pAObAE8DrE37IN7H+zaDDkBlc6ZNGX5pXop2AUPeQo3ZX 9BvqC+gyILNsZn2iinXHztB9mHVFPBjGzqNUee8Q= From: Fedor Pchelkin To: David Airlie , Daniel Vetter , Dave Airlie Cc: Fedor Pchelkin , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Daniel Stone , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Alexey Khoroshilov , lvc-project@linuxtesting.org Subject: [PATCH] drm/crtc: do not release uninitialized connector reference Date: Fri, 21 Jul 2023 13:15:59 +0300 Message-ID: <20230721101600.4392-1-pchelkin@ispras.ru> X-Mailer: git-send-email 2.41.0 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Inside drm_mode_setcrtc() connector_set is allocated using kmalloc_array() so its values are uninitialized. When filling this array with actual pointers to drm connector objects, an error caused with invalid ioctl request data may occur leading us to put references to already taken objects. However, the last elements of the array are left uninitialized which makes drm_connector_put() to be called with an invalid argument. We can obviously just initialize the array with kcalloc() but the current fix chose a slightly different way. The index of failing array element is known so just put references to the array members with lower indices. The temporary 'connector' pointer seems to be redundant as we can directly fill the connector_set elements and thus avoid unnecessary NULL assignments and checks. Found by Linux Verification Center (linuxtesting.org) with Syzkaller. Fixes: b164d31f50b2 ("drm/modes: add connector reference counting. (v2)") Signed-off-by: Fedor Pchelkin --- drivers/gpu/drm/drm_crtc.c | 22 ++++++++-------------- 1 file changed, 8 insertions(+), 14 deletions(-) diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c index df9bf3c9206e..2a29c3cf12de 100644 --- a/drivers/gpu/drm/drm_crtc.c +++ b/drivers/gpu/drm/drm_crtc.c @@ -709,7 +709,7 @@ int drm_mode_setcrtc(struct drm_device *dev, void *data, struct drm_mode_crtc *crtc_req =3D data; struct drm_crtc *crtc; struct drm_plane *plane; - struct drm_connector **connector_set =3D NULL, *connector; + struct drm_connector **connector_set =3D NULL; struct drm_framebuffer *fb =3D NULL; struct drm_display_mode *mode =3D NULL; struct drm_mode_set set; @@ -852,25 +852,22 @@ int drm_mode_setcrtc(struct drm_device *dev, void *da= ta, } =20 for (i =3D 0; i < crtc_req->count_connectors; i++) { - connector_set[i] =3D NULL; set_connectors_ptr =3D (uint32_t __user *)(unsigned long)crtc_req->set_= connectors_ptr; if (get_user(out_id, &set_connectors_ptr[i])) { ret =3D -EFAULT; goto out; } =20 - connector =3D drm_connector_lookup(dev, file_priv, out_id); - if (!connector) { + connector_set[i] =3D drm_connector_lookup(dev, file_priv, out_id); + if (!connector_set[i]) { DRM_DEBUG_KMS("Connector id %d unknown\n", out_id); ret =3D -ENOENT; goto out; } DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n", - connector->base.id, - connector->name); - - connector_set[i] =3D connector; + connector_set[i]->base.id, + connector_set[i]->name); } } =20 @@ -891,12 +888,9 @@ int drm_mode_setcrtc(struct drm_device *dev, void *dat= a, if (fb) drm_framebuffer_put(fb); =20 - if (connector_set) { - for (i =3D 0; i < crtc_req->count_connectors; i++) { - if (connector_set[i]) - drm_connector_put(connector_set[i]); - } - } + if (connector_set) + while (--i >=3D 0) + drm_connector_put(connector_set[i]); kfree(connector_set); drm_mode_destroy(dev, mode); =20 --=20 2.41.0