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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E6ADFC4332F for ; Tue, 14 Nov 2023 14:36:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233634AbjKNOgz (ORCPT ); Tue, 14 Nov 2023 09:36:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57054 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233548AbjKNOgZ (ORCPT ); Tue, 14 Nov 2023 09:36:25 -0500 Received: from relay1-d.mail.gandi.net (relay1-d.mail.gandi.net [217.70.183.193]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A31E310CE; Tue, 14 Nov 2023 06:36:02 -0800 (PST) Received: by mail.gandi.net (Postfix) with ESMTPA id C8742240002; Tue, 14 Nov 2023 14:35:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=gm1; t=1699972561; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=2K1mbcUA++OLwr4dR6O4Gp4Y1DTPQD4iQtrtg8iFg2o=; b=GHqnYtg8T4cVJRnGe93qe/5ni27eMDmGi3R9vt9cWVZa2wwLeZArrgmiaUdSjF7YxSMLFt blMt+5d8D5y/hSViLw/CLj0GNEZhD0y3jHUOTl4saf2JmJlQV359BfIgu76pXnXVYzc+2S tT6A4XYIomBR34ZVVy9AnLF09FN77TUWCDrbqe1HhbADq+IFK59sw8WzybjVGHQXe82A4P u+B4lQ1z/2uPRCV1N+mzMz5RqL/bMov7PZ+WOylCaV++7+vFCFERMqGWO+4Q0Un2lMmwe9 ojjEkKCAyzK3D4SeDApVoa+BO19ZFHPNqIsHHzeEXtuavzbTHTq2YBxPdSkQ2A== From: Herve Codina To: Saravana Kannan , Petr Mladek , Steven Rostedt , Andy Shevchenko , Rasmus Villemoes , Sergey Senozhatsky , Sakari Ailus , "Rafael J. Wysocki" Cc: linux-kernel@vger.kernel.org, Allan Nielsen , Horatiu Vultur , Steen Hegelund , Thomas Petazzoni , Herve Codina , stable@vger.kernel.org Subject: [PATCH v2 1/1] lib/vsprintf: Fix %pfwf when current node refcount == 0 Date: Tue, 14 Nov 2023 15:35:58 +0100 Message-ID: <20231114143558.356259-1-herve.codina@bootlin.com> X-Mailer: git-send-email 2.41.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-GND-Sasl: herve.codina@bootlin.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org A refcount issue can appeared in __fwnode_link_del() due to the pr_debug() call: WARNING: CPU: 0 PID: 901 at lib/refcount.c:25 refcount_warn_saturate+0xe5/0x110 Call Trace: ... of_node_get+0x1e/0x30 of_fwnode_get+0x28/0x40 fwnode_full_name_string+0x34/0x90 fwnode_string+0xdb/0x140 ... vsnprintf+0x17b/0x630 ... __fwnode_link_del+0x25/0xa0 fwnode_links_purge+0x39/0xb0 of_node_release+0xd9/0x180 ... Indeed, an fwnode (of_node) is being destroyed and so, of_node_release() is called because the of_node refcount reached 0. >From of_node_release() several function calls are done and lead to a pr_debug() calls with %pfwf to print the fwnode full name. The issue is not present if we change %pfwf to %pfwP. To print the full name, %pfwf iterates over the current node and its parents and obtain/drop a reference to all nodes involved. In order to allow to print the full name (%pfwf) of a node while it is being destroyed, do not obtain/drop a reference to this current node. Fixes: a92eb7621b9f ("lib/vsprintf: Make use of fwnode API to obtain node names and separators") Cc: stable@vger.kernel.org Signed-off-by: Herve Codina --- Changes v1 -> v2 - Avoid handling current node out of the loop. Instead obtain/drop references in the loop based on the depth value. - Remove some of the backtrace lines in the commit log. lib/vsprintf.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/lib/vsprintf.c b/lib/vsprintf.c index afb88b24fa74..633f5481ac17 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -2110,15 +2110,20 @@ char *fwnode_full_name_string(struct fwnode_handle *fwnode, char *buf, /* Loop starting from the root node to the current node. */ for (depth = fwnode_count_parents(fwnode); depth >= 0; depth--) { - struct fwnode_handle *__fwnode = - fwnode_get_nth_parent(fwnode, depth); + /* + * Only get a reference for other nodes (ie parents node). + * fwnode refcount may be 0 here. + */ + struct fwnode_handle *__fwnode = depth ? + fwnode_get_nth_parent(fwnode, depth) : fwnode; buf = string(buf, end, fwnode_get_name_prefix(__fwnode), default_str_spec); buf = string(buf, end, fwnode_get_name(__fwnode), default_str_spec); - fwnode_handle_put(__fwnode); + if (depth) + fwnode_handle_put(__fwnode); } return buf; -- 2.41.0