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=-8.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 5EB44C43441 for ; Wed, 10 Oct 2018 11:33:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EB6E521479 for ; Wed, 10 Oct 2018 11:33:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="qxwohb8I" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EB6E521479 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726728AbeJJSzL (ORCPT ); Wed, 10 Oct 2018 14:55:11 -0400 Received: from mail-pl1-f196.google.com ([209.85.214.196]:32785 "EHLO mail-pl1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726022AbeJJSzL (ORCPT ); Wed, 10 Oct 2018 14:55:11 -0400 Received: by mail-pl1-f196.google.com with SMTP id s4-v6so2418369plp.0 for ; Wed, 10 Oct 2018 04:33:27 -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:in-reply-to:references :mime-version:content-transfer-encoding; bh=m77aAX7nz09GGNKYMSeXlAxI5zFlcTR4XjjXk5bt2eE=; b=qxwohb8IeVIA6M+g1c3v9hx155YNdNAd2VHwbh8d5sw/B3Ymu9ksMYlkY9lfvzogIp DF1Z/lEH8gd9EhmulDVrD/R/kcaVYhZAHLRAzTqD/9v0f5sxEwXqMZ5hD0tzTWC5/MUv WmVn8jA09SWsdpBSrTEpHzdv40aDrY6AVnbZD0iDJZ96Q8XhrvD+/3Ip3t+Dt2L35dlS Frya4jzU7iv+Xd1QUGxVTm/YzmPBfLjDb5F7pZUe4GBhSffR9Qpy9F57WqnG6WlyQkrC SviQx5huyFUP3Q0b7k35Sj+dbE+of2eXXj7m3aUE2uchXPyQ0El9HduTojQ6JsWo1/pY dPTg== 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:in-reply-to :references:mime-version:content-transfer-encoding; bh=m77aAX7nz09GGNKYMSeXlAxI5zFlcTR4XjjXk5bt2eE=; b=RCGrseZeAmkvmP8Eq+kV/ODAqz0/Kd/x9R3n2tIJVIfeVvASkGK4DQN6YIxGe0AUbp efgSQ152DskaXYx1099Ys73+v1gUOgUnSPBEwD1S3mOIPedjeLcti7Hp8UphYxAs2OAY tVqc1FYbO+V/tvySAiBfAarb31rL21+MWsFQLoNxJ7dBqSUe90iDGWxIS3sNYfrQzkk+ niFH2Mj/izU3MoxXlKfmN1b+/afc63mJmjUoBOiY4+80XXyjC6ozOtMLiQdMAGZroJ74 uuEl5DaIjEdCgGLkcGtXxuJmKg+Kqc6ahGDHPHhAGfddz0Tz+TIP52KMnpcqSBVMzKiv Jfaw== X-Gm-Message-State: ABuFfoiFkdmV5zQT2uUzgewn8HxAdgIaF9f2uLF3yiGjfCmmCxKvSJCg iHgyQtoHsycW32r4pxSTWCY= X-Google-Smtp-Source: ACcGV60joCZSMsg6r2tZmtffUQk6QVTe95G/lfzFBKZlizN2pTy88EJaGB3mtPnXersLR68RWAYwyA== X-Received: by 2002:a17:902:a618:: with SMTP id u24-v6mr32577422plq.77.1539171206972; Wed, 10 Oct 2018 04:33:26 -0700 (PDT) Received: from localhost.localdomain ([121.137.63.184]) by smtp.gmail.com with ESMTPSA id g5-v6sm36349514pfk.160.2018.10.10.04.33.22 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 10 Oct 2018 04:33:26 -0700 (PDT) From: Sergey Senozhatsky To: Steven Rostedt , Petr Mladek Cc: linux-kernel@vger.kernel.org, Sergey Senozhatsky , Sergey Senozhatsky Subject: [PATCH] printk: fix integer overflow in setup_log_buf() Date: Wed, 10 Oct 2018 20:33:08 +0900 Message-Id: <20181010113308.9337-1-sergey.senozhatsky@gmail.com> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20181010103808.882-1-sergey.senozhatsky@gmail.com> References: <20181010103808.882-1-sergey.senozhatsky@gmail.com> 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 The way we calculate logbuf free space percentage overflows signed integer: int free; free = __LOG_BUF_LEN - log_next_idx; pr_info("early log buf free: %u(%u%%)\n", free, (free * 100) / __LOG_BUF_LEN); We support LOG_BUF_LEN of up to 1<<25 bytes. Since setup_log_buf() is called during early init, logbuf is mostly empty, so __LOG_BUF_LEN - log_next_idx is close to 1<<25. Thus when we multiply it by 100, we overflow signed integer value range: 100 is 2^6 + 2^5 + 2^2. Example, booting with LOG_BUF_LEN 1<<25 and log_buf_len=2G boot param: [ 0.075317] log_buf_len: -2147483648 bytes [ 0.075319] early log buf free: 33549896(-28%) Make "free" unsigned integer and use appropriate printk() specifier. Signed-off-by: Sergey Senozhatsky --- kernel/printk/printk.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index c3f0e3927e77..c9e1d3bf695e 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -1083,7 +1083,7 @@ void __init setup_log_buf(int early) { unsigned long flags; char *new_log_buf; - int free; + unsigned int free; if (log_buf != __log_buf) return; @@ -1116,8 +1116,8 @@ void __init setup_log_buf(int early) memcpy(log_buf, __log_buf, __LOG_BUF_LEN); logbuf_unlock_irqrestore(flags); - pr_info("log_buf_len: %d bytes\n", log_buf_len); - pr_info("early log buf free: %d(%d%%)\n", + pr_info("log_buf_len: %u bytes\n", log_buf_len); + pr_info("early log buf free: %u(%u%%)\n", free, (free * 100) / __LOG_BUF_LEN); } -- 2.19.1