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 DBC38C982E1 for ; Mon, 21 Sep 2026 07:24:12 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 37A5910E16C; Mon, 21 Sep 2026 07:24:12 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=bootlin.com header.i=@bootlin.com header.b="CF4oYu2f"; dkim-atps=neutral Received: from smtpout-04.galae.net (smtpout-04.galae.net [185.171.202.116]) by gabe.freedesktop.org (Postfix) with ESMTPS id 51F2D10E16C for ; Mon, 21 Sep 2026 07:24:11 +0000 (UTC) Received: from smtpout-01.galae.net (smtpout-01.galae.net [212.83.139.233]) by smtpout-04.galae.net (Postfix) with ESMTPS id 97D1BC2C65D; Mon, 21 Sep 2026 07:24:55 +0000 (UTC) Received: from mail.galae.net (mail.galae.net [212.83.136.155]) by smtpout-01.galae.net (Postfix) with ESMTPS id 7AB9F60339; Mon, 21 Sep 2026 07:24:09 +0000 (UTC) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 1BA8610328F4D; Mon, 21 Sep 2026 09:23:56 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim; t=1789975447; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:references; bh=RG0d/rWWwG5EWi14PZmG5qQITNqAdcjhf3I0KoA9dFs=; b=CF4oYu2f2Fb/6/P7G2edz+XGRaxwUM5y+QalfFftYc0K9ACk3pKG19v1Um+gp+onLXLOAJ XIWebq+ZnBsUGIWQ/NZNNkbdrZLZrg9SmIbGwpb8GFep47g3S359CAIOawHvPUMBfq002u 5YsxQvNUoAdJlltQ+8pJAMoO9OeuxcUunDnEDL25IhJ6iIvH4yM+gdd0dcHzAnw7Kf6JMb wffUF0B8jCFMuYKQjMW1VJ8wgJntfoU7V5WjeW6JE1H9DxBVy0+KgqXljo4rgC0CUOy6tI vl2QvKL5UETgKy276ScNoF4LORkAjcvyc021rRxRFh4Sb/93oVLYRy/9WfDKZg== Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Mon, 21 Sep 2026 09:23:55 +0200 Message-Id: Subject: Re: [PATCH v11 14/74] drm/bridge: Fix unlocked list access in drm_bridge_attach() Cc: , , , , , , To: "Cristian Ciocaltea" , "Maarten Lankhorst" , "Maxime Ripard" , "Thomas Zimmermann" , "David Airlie" , "Simona Vetter" , "Dave Stevenson" , "Dmitry Baryshkov" , "Andrzej Hajda" , "Neil Armstrong" , "Robert Foss" , "Laurent Pinchart" , "Jonas Karlman" , "Jernej Skrabec" , "Luca Ceresoli" , "Chen-Yu Tsai" , "Samuel Holland" , =?utf-8?q?Ma=C3=ADra_Canal?= , "Raspberry Pi Kernel Maintenance" , "Raphael Gallais-Pou" , "Sandy Huang" , =?utf-8?q?Heiko_St=C3=BCbner?= , "Andy Yan" , "Algea Cao" , "Daniel Stone" , "Liu Ying" , "Phong LE" , "Helge Deller" From: "Luca Ceresoli" X-Mailer: aerc 0.22.0 References: <20260901-dw-hdmi-qp-scramb-v11-0-bc12954a0688@collabora.com> <20260901-dw-hdmi-qp-scramb-v11-14-bc12954a0688@collabora.com> In-Reply-To: <20260901-dw-hdmi-qp-scramb-v11-14-bc12954a0688@collabora.com> X-Last-TLS-Session-Version: TLSv1.3 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Tue Sep 1, 2026 at 8:50 PM CEST, Cristian Ciocaltea wrote: > drm_bridge_attach() inspects bridge->list to warn about bridges being > attached without a previous drm_bridge_add() call, but it does so > without holding bridge_lock. > > The list head can be concurrently written by drm_bridge_add(), > drm_bridge_remove() and __drm_bridge_free() while they operate on > neighbouring entries of bridge_list or bridge_lingering_list, all of > them under bridge_lock. Hence the unlocked read is a data race, even > though it is unlikely to change the outcome of list_empty() in practice. > > Perform the check with bridge_lock held. > > Fixes: 76f1a9711b83 ("drm/bridge: add warning for bridges attached withou= t being added") > Signed-off-by: Cristian Ciocaltea Reviewed-by: Luca Ceresoli -- Luca Ceresoli, Bootlin Embedded Linux and Kernel engineering https://bootlin.com