From patchwork Fri Jul 17 14:02:04 2026 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Albert Esteve X-Patchwork-Id: 2674 Return-Path: X-Original-To: noreply@patchwork.local Delivered-To: noreply@patchwork.local Received: from sin.lore.kernel.org (sin.lore.kernel.org [104.64.211.4]) by mxe881.netcup.net (Postfix) with ESMTPS id 9FF801C2B6A for ; Fri, 17 Jul 2026 16:03:41 +0200 (CEST) Authentication-Results: mxe881; dkim=pass header.d=redhat.com; spf=pass (sender IP is 104.64.211.4) smtp.mailfrom=linux-sunxi+bounces-24484-noreply=patchwork.local@lists.linux.dev smtp.helo=sin.lore.kernel.org Received-SPF: pass (mxe881: domain of lists.linux.dev designates 104.64.211.4 as permitted sender) client-ip=104.64.211.4; envelope-from=linux-sunxi+bounces-24484-noreply=patchwork.local@lists.linux.dev; helo=sin.lore.kernel.org; Received: from smtp.subspace.kernel.org (conduit.subspace.kernel.org [100.90.174.1]) by sin.lore.kernel.org (Postfix) with ESMTP id 7BE0F3000580 for ; Fri, 17 Jul 2026 14:03:21 +0000 (UTC) Received: from localhost.localdomain (localhost.localdomain [127.0.0.1]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 8FFE23DDAEC; Fri, 17 Jul 2026 14:03:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Tp1Ny1sh" X-Original-To: linux-sunxi@lists.linux.dev Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0210642902C for ; Fri, 17 Jul 2026 14:03:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784297000; cv=none; b=VX9VwlGMh4kKJQ29z4nx4q2iqgcyOSy+BLVWyfV/eh6kD05+Er7fo6cFEdQ7AX/vgvamKMKg1w2rzaW+F+F0rgOBc50SmPaQ3bJixsp8Q0pwv29P6l03UYKk+V0EMcG0hoUnWLXCtT4Jkxo3ap+jDpNhPxmKw97w0N93kSF3yl0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784297000; c=relaxed/simple; bh=FTIUpYJulTDPMntpPJg3cHAwQl8IpGYir+ZH1v5UeXQ=; h=From:Date:Subject:MIME-Version:Message-Id:References:In-Reply-To: To:Cc:Content-Type; b=PDIB1MhxWYOc4prLJrB+4DOuMcZCTb8/BEjnT3u5sXTJKoNXTXWd4rRKzwI29eJvbjpJB4khW3KA2620n7p89mSLF+LlIKRuDGtx2KVuEbAT2QfTywvcOgocWA9ln80xabDMw/y40XcDp4/M0dvWUe4WCo5ugteSQFXFb87+ozs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=Tp1Ny1sh; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1784296988; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=VGJka35hl1u+NTZhYLLi9zxEwwQ2DlQIwAaKGDObA0o=; b=Tp1Ny1shhyRLAmBWt0fPAJiWkBvxTPbYEf5Bq5XJFtnrrAE+KtK872rBrQmPz+PPa6UGv9 J8/d2i4neIXX5DoaDUnkYqTn3RVL1jHIvO6Fzt9mMlKF5tt8zbCPO/z98AeKQNzqUxrxvI G6XJuXeQC8xX+yV16FnQhlRmcFUvQP8= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-1-xZKcB7tRNWWXh1oZfo_uWA-1; Fri, 17 Jul 2026 10:03:04 -0400 X-MC-Unique: xZKcB7tRNWWXh1oZfo_uWA-1 X-Mimecast-MFC-AGG-ID: xZKcB7tRNWWXh1oZfo_uWA_1784296976 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 0FDE8180074B; Fri, 17 Jul 2026 14:02:55 +0000 (UTC) Received: from [192.168.1.153] (headnet05.pony-001.prod.iad2.dc.redhat.com [10.2.32.117]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 39396180025B; Fri, 17 Jul 2026 14:02:38 +0000 (UTC) From: Albert Esteve Date: Fri, 17 Jul 2026 16:02:04 +0200 Subject: [PATCH v3 1/4] drm/panel: have drm_panel_add/remove manage a list reference Precedence: bulk X-Mailing-List: linux-sunxi@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20260717-drm_refcount_wiring-v3-1-023900c32e01@redhat.com> References: <20260717-drm_refcount_wiring-v3-0-023900c32e01@redhat.com> In-Reply-To: <20260717-drm_refcount_wiring-v3-0-023900c32e01@redhat.com> To: Neil Armstrong , Jessica Zhang , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Andrzej Hajda , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Luca Ceresoli , Inki Dae , Jagan Teki , Marek Szyprowski , Laurentiu Palcu , Lucas Stach , Frank Li , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , Paul Cercueil , Linus Walleij , Marek Vasut , Stefan Agner , Tomi Valkeinen , Laurent Pinchart , Kieran Bingham , Geert Uytterhoeven , Magnus Damm , Biju Das , Sandy Huang , =?utf-8?q?Heiko_St=C3=BCbner?= , Andy Yan , Yannick Fertre , Raphael Gallais-Pou , Philippe Cornu , Maxime Coquelin , Alexandre Torgue , Chen-Yu Tsai , Samuel Holland , Jyri Sarha , Jingoo Han , Seung-Woo Kim , Kyungmin Park , Krzysztof Kozlowski , Peter Griffin , Alim Akhtar , Alison Wang , Paul Kocialkowski , Alain Volmat , Raphael Gallais-Pou , Thierry Reding , Mikko Perttunen , Jonathan Hunter Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-rockchip@lists.infradead.org, linux-stm32@st-md-mailman.stormreply.com, linux-sunxi@lists.linux.dev, linux-samsung-soc@vger.kernel.org, linux-tegra@vger.kernel.org, Albert Esteve X-Developer-Signature: v=1; a=ed25519-sha256; t=1784296938; l=1577; i=aesteve@redhat.com; s=20260303; h=from:subject:message-id; bh=FTIUpYJulTDPMntpPJg3cHAwQl8IpGYir+ZH1v5UeXQ=; b=YrbusurGGSB7YvjF6ZccKN+vcKVUHQpfLac942+Cranf6atmGaR9SI9po6YBiflKgqH3V3Uoc fE7eQSMY2CcDc+mWaONJx9YbrBOGvZ4cSQGsIw9XOJoVNKgKBXhpN1g X-Developer-Key: i=aesteve@redhat.com; a=ed25519; pk=YSFz6sOHd2L45+Fr8DIvHTi6lSIjhLZ5T+rkxspJt1s= X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: -B74fcN81Ou7cIBVg-pRgtSEIitygmU53z815yId_gI_1784296976 X-Mimecast-Originator: redhat.com X-MORS-Enabled: yes X-MORS-DOMAIN: patchwork.local X-MORS-HOSTING: hosting172546 X-MORS-USER: hosting172546 X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= The global panel_list holds raw pointers to drm_panel objects. Nothing prevents a panel from being freed while it is still linked in the list: if a driver's probe calls drm_panel_add() and then fails at a later step, panel->list remains in panel_list. Any subsequent call to of_drm_find_panel() that iterates the list will dereference freed memory. Have drm_panel_add() acquire a reference via drm_panel_get() before inserting the panel into the list, and have drm_panel_remove() drop it via drm_panel_put() after removing the panel from the list. The global registry now holds a counted reference for as long as the panel is listed, ensuring the object outlives any concurrent lookup. Reviewed-by: Maxime Ripard Signed-off-by: Albert Esteve Reviewed-by: Luca Ceresoli --- drivers/gpu/drm/drm_panel.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c index 2c5649e433dfb..545fe93dc28fe 100644 --- a/drivers/gpu/drm/drm_panel.c +++ b/drivers/gpu/drm/drm_panel.c @@ -81,6 +81,7 @@ static void drm_panel_init(struct drm_panel *panel, struct device *dev, */ void drm_panel_add(struct drm_panel *panel) { + drm_panel_get(panel); mutex_lock(&panel_lock); list_add_tail(&panel->list, &panel_list); mutex_unlock(&panel_lock); @@ -98,6 +99,7 @@ void drm_panel_remove(struct drm_panel *panel) mutex_lock(&panel_lock); list_del_init(&panel->list); mutex_unlock(&panel_lock); + drm_panel_put(panel); } EXPORT_SYMBOL(drm_panel_remove);