From patchwork Mon Mar 31 02:24:13 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Anusha Srivatsa X-Patchwork-Id: 14033152 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 8645DC36010 for ; Mon, 31 Mar 2025 03:25:57 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id EE39E10E375; Mon, 31 Mar 2025 03:25:56 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.b="b10tsQkJ"; dkim-atps=neutral Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by gabe.freedesktop.org (Postfix) with ESMTPS id C6F7F10E2B0 for ; Mon, 31 Mar 2025 03:25:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1743391552; 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=5T/7FftKdPKD3W/7jWlPs9qhLB+6a9D8aoiBDQmOjYo=; b=b10tsQkJG+1B3E4jQ3hpgBIApVtfiKey/ThgrHGTOwaL2eE9LXs3bK/RxtIRDVUVJvsbJD /vyiB+WHf65sk7f3XEFCZ6NLq+weHYRddVR2YdZqA26N34WNiM7MQc6rO3pslTHPkDZiS5 6vTWSsQsW+jzes4Lit4SChMNLw3ie+8= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-625-S2nStVIvNkqmhWULI7WxbA-1; Sun, 30 Mar 2025 23:25:48 -0400 X-MC-Unique: S2nStVIvNkqmhWULI7WxbA-1 X-Mimecast-MFC-AGG-ID: S2nStVIvNkqmhWULI7WxbA_1743391546 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-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id B349C1933B49; Mon, 31 Mar 2025 03:25:46 +0000 (UTC) Received: from asrivats-na.rmtustx.csb (unknown [10.2.16.30]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 4774A180174E; Mon, 31 Mar 2025 03:25:44 +0000 (UTC) From: Anusha Srivatsa Date: Sun, 30 Mar 2025 22:24:13 -0400 Subject: [PATCH v3 2/4] drm/panel: Add refcount support MIME-Version: 1.0 Message-Id: <20250330-b4-panel-refcounting-v3-2-0e0d4e4641eb@redhat.com> References: <20250330-b4-panel-refcounting-v3-0-0e0d4e4641eb@redhat.com> In-Reply-To: <20250330-b4-panel-refcounting-v3-0-0e0d4e4641eb@redhat.com> To: Neil Armstrong , Jessica Zhang , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Luca Ceresoli , Anusha Srivatsa X-Developer-Signature: v=1; a=ed25519-sha256; t=1743387855; l=4525; i=asrivats@redhat.com; s=20250122; h=from:subject:message-id; bh=DoR5/VZXVBzYD8Bh9VJZWzLpSoYgFBcfigl+6Gt4zx4=; b=4CAI971VEyiUDlrEtz01eKkDBl51GU09h8i8iBx/+HRNuGtU7iFqbFoo9zK0LVoRPwCxw0WY0 8ZoBs4vg5gXBGX6AAHv7871kpUDNB4qtg29xjZCl8CEBtlpnxnJsHFW X-Developer-Key: i=asrivats@redhat.com; a=ed25519; pk=brnIHkBsUZEhyW6Zyn0U92AeIZ1psws/q8VFbIkf1AU= X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 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" Allocate panel via reference counting. Add _get() and _put() helper functions to ensure panel allocations are refcounted. Avoid use after free by ensuring panel pointer is valid and can be usable till the last reference is put. Reviewed-by: Luca Ceresoli Reviewed-by: Maxime Ripard Signed-off-by: Anusha Srivatsa --- v3: Add include in this patch (Luca) v2: Export drm_panel_put/get() (Maxime) - Change commit log with better workding (Luca, Maxime) - Change drm_panel_put() to return void (Luca) - Code Cleanups - add return in documentation, replace bridge to panel (Luca) --- drivers/gpu/drm/drm_panel.c | 64 ++++++++++++++++++++++++++++++++++++++++++++- include/drm/drm_panel.h | 15 +++++++++++ 2 files changed, 78 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c index bdeab5710ee324dc1742fbc77582250960556308..7b17531d85a4dc3031709919564d2e4d8332f748 100644 --- a/drivers/gpu/drm/drm_panel.c +++ b/drivers/gpu/drm/drm_panel.c @@ -355,24 +355,86 @@ struct drm_panel *of_drm_find_panel(const struct device_node *np) } EXPORT_SYMBOL(of_drm_find_panel); +static void __drm_panel_free(struct kref *kref) +{ + struct drm_panel *panel = container_of(kref, struct drm_panel, refcount); + + kfree(panel->container); +} + +/** + * drm_panel_get - Acquire a panel reference + * @panel: DRM panel + * + * This function increments the panel's refcount. + * Returns: + * Pointer to @panel + */ +struct drm_panel *drm_panel_get(struct drm_panel *panel) +{ + if (!panel) + return panel; + + kref_get(&panel->refcount); + + return panel; +} +EXPORT_SYMBOL(drm_panel_get); + +/** + * drm_panel_put - Release a panel reference + * @panel: DRM panel + * + * This function decrements the panel's reference count and frees the + * object if the reference count drops to zero. + */ +void drm_panel_put(struct drm_panel *panel) +{ + if (panel) + kref_put(&panel->refcount, __drm_panel_free); +} +EXPORT_SYMBOL(drm_panel_put); + +/** + * drm_panel_put_void - wrapper to drm_panel_put() taking a void pointer + * + * @data: pointer to @struct drm_panel, cast to a void pointer + * + * Wrapper of drm_panel_put() to be used when a function taking a void + * pointer is needed, for example as a devm action. + */ +static void drm_panel_put_void(void *data) +{ + struct drm_panel *panel = (struct drm_panel *)data; + + drm_panel_put(panel); +} + void *__devm_drm_panel_alloc(struct device *dev, size_t size, size_t offset, const struct drm_panel_funcs *funcs, int connector_type) { void *container; struct drm_panel *panel; + int err; if (!funcs) { dev_warn(dev, "Missing funcs pointer\n"); return ERR_PTR(-EINVAL); } - container = devm_kzalloc(dev, size, GFP_KERNEL); + container = kzalloc(size, GFP_KERNEL); if (!container) return ERR_PTR(-ENOMEM); panel = container + offset; + panel->container = container; panel->funcs = funcs; + kref_init(&panel->refcount); + + err = devm_add_action_or_reset(dev, drm_panel_put_void, panel); + if (err) + return ERR_PTR(err); drm_panel_init(panel, dev, funcs, connector_type); diff --git a/include/drm/drm_panel.h b/include/drm/drm_panel.h index 97a5457b64fbbe9c91c6a4f41b8e1fbfe4fa604e..095e03c6e660d838b227e7a5cf8ca9b88c4bdc3d 100644 --- a/include/drm/drm_panel.h +++ b/include/drm/drm_panel.h @@ -28,6 +28,7 @@ #include #include #include +#include struct backlight_device; struct dentry; @@ -266,6 +267,17 @@ struct drm_panel { * If true then the panel has been enabled. */ bool enabled; + + /** + * @container: Pointer to the private driver struct embedding this + * @struct drm_panel. + */ + void *container; + + /** + * @refcount: reference count of users referencing this panel. + */ + struct kref refcount; }; void *__devm_drm_panel_alloc(struct device *dev, size_t size, size_t offset, @@ -296,6 +308,9 @@ void drm_panel_init(struct drm_panel *panel, struct device *dev, const struct drm_panel_funcs *funcs, int connector_type); +struct drm_panel *drm_panel_get(struct drm_panel *panel); +void drm_panel_put(struct drm_panel *panel); + void drm_panel_add(struct drm_panel *panel); void drm_panel_remove(struct drm_panel *panel);