From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 0F5DD34AB17; Tue, 11 Nov 2025 01:42:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762825348; cv=none; b=GqM1kL4UkAnxbP21HNnQ00oiv94mjInQ3OmEYh4NE1BFZ13pcUWsl4OpqTOJPNAbC4i1ROGK5mj7LYIF6qnHcpZ8BgfjPI6aeDvJahaQvnVifAmYgNIJ1UCjnMrxrpWdLgrU+azaOqtI8/Z2W8WqxxLz/VD6Fk3m2yuWcCz7L/w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762825348; c=relaxed/simple; bh=yG+4QglGZly4MlQxYvMKUR0MLTYciggiEISa+S233f8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=HgiQc+E5rrCLZA2aIkm0B5hc86YL9NMhJwVyUCMa4C4x1HqXapJU+JkwmGd4IPUdKwsBIAVlRFfjLWJJUBdJgkMuywXP71g48oxH1G/CDW7N8JkPGPQb+tbqyqxrltGAKGBDEpPyi5zVG2tJw789/16dyHs3fu1YcLPhnRg5aSc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=bz79IJNs; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="bz79IJNs" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 581DFC19422; Tue, 11 Nov 2025 01:42:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1762825347; bh=yG+4QglGZly4MlQxYvMKUR0MLTYciggiEISa+S233f8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bz79IJNsYTwdLWDA3Z8vIb94E7UrBdHUCyg88C6l73KsHOZl5u5ndOHadgq4I3qVL VhfydA7T3ZZOhKHk0SHYgY8fqCqWPm7ceW/AHtgYsUcbmmniL+XaN0WjYBjRn+elBQ zbisXd2eA9Xwc1UH6o8fAy7d8xq2acG9XBLuHOuE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Gustavo Luiz Duarte , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.17 765/849] netconsole: Acquire su_mutex before navigating configs hierarchy Date: Tue, 11 Nov 2025 09:45:35 +0900 Message-ID: <20251111004554.926967084@linuxfoundation.org> X-Mailer: git-send-email 2.51.2 In-Reply-To: <20251111004536.460310036@linuxfoundation.org> References: <20251111004536.460310036@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.17-stable review patch. If anyone has any objections, please let me know. ------------------ From: Gustavo Luiz Duarte [ Upstream commit d7d2fcf7ae31471b4e08b7e448b8fd0ec2e06a1b ] There is a race between operations that iterate over the userdata cg_children list and concurrent add/remove of userdata items through configfs. The update_userdata() function iterates over the nt->userdata_group.cg_children list, and count_extradata_entries() also iterates over this same list to count nodes. Quoting from Documentation/filesystems/configfs.rst: > A subsystem can navigate the cg_children list and the ci_parent pointer > to see the tree created by the subsystem. This can race with configfs' > management of the hierarchy, so configfs uses the subsystem mutex to > protect modifications. Whenever a subsystem wants to navigate the > hierarchy, it must do so under the protection of the subsystem > mutex. Without proper locking, if a userdata item is added or removed concurrently while these functions are iterating, the list can be accessed in an inconsistent state. For example, the list_for_each() loop can reach a node that is being removed from the list by list_del_init() which sets the nodes' .next pointer to point to itself, so the loop will never end (or reach the WARN_ON_ONCE in update_userdata() ). Fix this by holding the configfs subsystem mutex (su_mutex) during all operations that iterate over cg_children. This includes: - userdatum_value_store() which calls update_userdata() to iterate over cg_children - All sysdata_*_enabled_store() functions which call count_extradata_entries() to iterate over cg_children The su_mutex must be acquired before dynamic_netconsole_mutex to avoid potential lock ordering issues, as configfs operations may already hold su_mutex when calling into our code. Fixes: df03f830d099 ("net: netconsole: cache userdata formatted string in netconsole_target") Signed-off-by: Gustavo Luiz Duarte Link: https://patch.msgid.link/20251029-netconsole-fix-warn-v1-1-0d0dd4622f48@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- drivers/net/netconsole.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c index e3722de08ea9f..3ff1dfc3d26b2 100644 --- a/drivers/net/netconsole.c +++ b/drivers/net/netconsole.c @@ -928,6 +928,7 @@ static ssize_t userdatum_value_store(struct config_item *item, const char *buf, if (count > MAX_EXTRADATA_VALUE_LEN) return -EMSGSIZE; + mutex_lock(&netconsole_subsys.su_mutex); mutex_lock(&dynamic_netconsole_mutex); ret = strscpy(udm->value, buf, sizeof(udm->value)); @@ -941,6 +942,7 @@ static ssize_t userdatum_value_store(struct config_item *item, const char *buf, ret = count; out_unlock: mutex_unlock(&dynamic_netconsole_mutex); + mutex_unlock(&netconsole_subsys.su_mutex); return ret; } @@ -966,6 +968,7 @@ static ssize_t sysdata_msgid_enabled_store(struct config_item *item, if (ret) return ret; + mutex_lock(&netconsole_subsys.su_mutex); mutex_lock(&dynamic_netconsole_mutex); curr = !!(nt->sysdata_fields & SYSDATA_MSGID); if (msgid_enabled == curr) @@ -986,6 +989,7 @@ static ssize_t sysdata_msgid_enabled_store(struct config_item *item, ret = strnlen(buf, count); unlock: mutex_unlock(&dynamic_netconsole_mutex); + mutex_unlock(&netconsole_subsys.su_mutex); return ret; } @@ -1000,6 +1004,7 @@ static ssize_t sysdata_release_enabled_store(struct config_item *item, if (ret) return ret; + mutex_lock(&netconsole_subsys.su_mutex); mutex_lock(&dynamic_netconsole_mutex); curr = !!(nt->sysdata_fields & SYSDATA_RELEASE); if (release_enabled == curr) @@ -1020,6 +1025,7 @@ static ssize_t sysdata_release_enabled_store(struct config_item *item, ret = strnlen(buf, count); unlock: mutex_unlock(&dynamic_netconsole_mutex); + mutex_unlock(&netconsole_subsys.su_mutex); return ret; } @@ -1034,6 +1040,7 @@ static ssize_t sysdata_taskname_enabled_store(struct config_item *item, if (ret) return ret; + mutex_lock(&netconsole_subsys.su_mutex); mutex_lock(&dynamic_netconsole_mutex); curr = !!(nt->sysdata_fields & SYSDATA_TASKNAME); if (taskname_enabled == curr) @@ -1054,6 +1061,7 @@ static ssize_t sysdata_taskname_enabled_store(struct config_item *item, ret = strnlen(buf, count); unlock: mutex_unlock(&dynamic_netconsole_mutex); + mutex_unlock(&netconsole_subsys.su_mutex); return ret; } @@ -1069,6 +1077,7 @@ static ssize_t sysdata_cpu_nr_enabled_store(struct config_item *item, if (ret) return ret; + mutex_lock(&netconsole_subsys.su_mutex); mutex_lock(&dynamic_netconsole_mutex); curr = !!(nt->sysdata_fields & SYSDATA_CPU_NR); if (cpu_nr_enabled == curr) @@ -1097,6 +1106,7 @@ static ssize_t sysdata_cpu_nr_enabled_store(struct config_item *item, ret = strnlen(buf, count); unlock: mutex_unlock(&dynamic_netconsole_mutex); + mutex_unlock(&netconsole_subsys.su_mutex); return ret; } -- 2.51.0