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 X-Spam-Level: X-Spam-Status: No, score=-2.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 38AFDC10F14 for ; Tue, 23 Apr 2019 06:25:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0179C206BA for ; Tue, 23 Apr 2019 06:25:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="igxoj6e4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726026AbfDWGZV (ORCPT ); Tue, 23 Apr 2019 02:25:21 -0400 Received: from mail-pg1-f193.google.com ([209.85.215.193]:44392 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725882AbfDWGZU (ORCPT ); Tue, 23 Apr 2019 02:25:20 -0400 Received: by mail-pg1-f193.google.com with SMTP id z16so2437112pgv.11 for ; Mon, 22 Apr 2019 23:25:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=RaaGcTzhI0SDxCVukGPZqJTxviymuimG+0pW1Zook1E=; b=igxoj6e4d71VSplvzcgfh/aXS5Wto6zRfIlI4XOE5i8Bnx/GEe9uRgV03C3nI74NJN gFdXkhYgHOjTCoGgA3oU8xYt1T7p8+ZsOcrTQFMY7o4odCLvaV/9mj81539a9DjXOuIG bGGc9WTC/dxH/BorS7ZcGgpGpEVuKBxxIBR41yms2fHLREMT+2dKVl89Lfnzms2TUosr UtEFeeWyV1+CPNa2hOdRzuLrwo8zZbXydw5UErHsL0FfPpgmWcJkUuOsL8es3gEaR3eB a+v0rQnBFLfVg/WLW9qOpzWRQffTtSuNPI1WofXymJiZfoqSpF2hGDg2s/9wjqEU7z1e vDlg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=RaaGcTzhI0SDxCVukGPZqJTxviymuimG+0pW1Zook1E=; b=D+DDQUt2P7cXILWuKUTrkVqByKHvhV4C3tAC3OskYb9kjzT0D4maDlpKLXLqx99m3Q nRvRm1HFSN6L4sLoxn+Qlv6q9nJvjjzXoH6WK74k59S5KwRR8EtjVo1dZ+idFW70VVuI Vv/KVNKXGBhCVJ+uLE/eA7VgHqVHOCSsogmMv2/+5ulyoT1HdDg5pk+EhQ+h6aXBL6eh ih6yQpjdMYO/+oorqbyG6IVWJXTzlEG9LOM8HtHpQ2tgXoywpdqKpWUS4VpjM6mdkuzd wyIlob49+4fvKH9FIIqDUgD1LI97qfDF3FyYhB7f7oAsF5kmBubx0lGnuWkvYfm66JsP rPiA== X-Gm-Message-State: APjAAAV6WaTs2U6X/fnexTZMxxfc043p5e1LlSl3csJ25NhNEFQnInSx oOoz467HVOPqhLHv42WDkpRtuw4A X-Google-Smtp-Source: APXvYqwzarnB9xzUvmDFbCaK6QbmtaL/b+1tiKSulvpSp5SthU6MKKBTjfMfITjKnKNT9Qx4hfZs6w== X-Received: by 2002:aa7:9a99:: with SMTP id w25mr2567796pfi.240.1556000719974; Mon, 22 Apr 2019 23:25:19 -0700 (PDT) Received: from localhost.localdomain ([175.223.38.143]) by smtp.gmail.com with ESMTPSA id p3sm19490287pfn.167.2019.04.22.23.25.16 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 22 Apr 2019 23:25:19 -0700 (PDT) From: Sergey Senozhatsky X-Google-Original-From: Sergey Senozhatsky To: Petr Mladek , Steven Rostedt Cc: Andrew Morton , linux-kernel@vger.kernel.org, Sergey Senozhatsky , Sergey Senozhatsky Subject: [RFC][PATCH 0/2] Access console drivers list under console_sem Date: Tue, 23 Apr 2019 15:25:09 +0900 Message-Id: <20190423062511.1118-1-sergey.senozhatsky@gmail.com> X-Mailer: git-send-email 2.21.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Petr, Steven, RFC Normally, we grab console_sem lock before we iterate consoles list, which is necessary if we want to be race free. The only exception to this rule is console_flush_on_panic(). However, it seems that we are not fully race free - register_console() iterates console drivers list in unsafe manner in several places. E.g. the following scenarion: CPU0 CPU1 register_console() unregister_console() console_lock() for_each_console() // modify console_drivers con->foo kfree(con) So I have two quick-n-dirty patches, which remove unsafe console list access. What do you think? Sergey Senozhatsky (2): printk: lock console_sem before we unregister boot consoles printk: take console_sem when accessing console drivers list kernel/printk/printk.c | 117 ++++++++++++++++++++++++----------------- 1 file changed, 69 insertions(+), 48 deletions(-) -- 2.21.0