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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 A4064C432C3 for ; Sat, 16 Nov 2019 16:15:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7AA8B21823 for ; Sat, 16 Nov 2019 16:15:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573920933; bh=5l/Xgde1Gjo6tTxZxmJhq3kWiXZSn2Yb5xa1Efq5ueE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=gH0tbHVPxh0/cvFawfw0UqL3kI8OiESCjILnA4VHs1MdrRramIobjYHLAAxdT3Igu OWjSiaKXSGNFMzNPid7XeeejGT0R+/nV6T7H38xsBsVR/JRdfXYmBln1QF4znnI5og 1ztUtMq3DmS6EZJ9NHSfotqoZhb6CMHNzQdxgv/8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731943AbfKPQPb (ORCPT ); Sat, 16 Nov 2019 11:15:31 -0500 Received: from mail.kernel.org ([198.145.29.99]:54192 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729706AbfKPPrb (ORCPT ); Sat, 16 Nov 2019 10:47:31 -0500 Received: from sasha-vm.mshome.net (unknown [50.234.116.4]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5215A20857; Sat, 16 Nov 2019 15:47:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573919250; bh=5l/Xgde1Gjo6tTxZxmJhq3kWiXZSn2Yb5xa1Efq5ueE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qRvDxALONoOCSEX0jICE1bJux8bXyWBak76IGGVIdHk+5BqS94pEBvc64zpDjikyp 83XpYRYCGNAekUCDtH/aCi7iw/l7BvjHaGaUuy3RwjX4EP3aX4CzF9KrdU4L0hkhns bnuTlUiIcPZIug0ExUJSaVFxsI25kPU/N2kqVF5w= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Sergey Senozhatsky , Sergey Senozhatsky , Petr Mladek , Sasha Levin Subject: [PATCH AUTOSEL 4.14 002/150] printk: fix integer overflow in setup_log_buf() Date: Sat, 16 Nov 2019 10:45:00 -0500 Message-Id: <20191116154729.9573-2-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191116154729.9573-1-sashal@kernel.org> References: <20191116154729.9573-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Sergey Senozhatsky [ Upstream commit d2130e82e9454304e9b91ba9da551b5989af8c27 ] 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. Link: http://lkml.kernel.org/r/20181010113308.9337-1-sergey.senozhatsky@gmail.com To: Steven Rostedt Cc: linux-kernel@vger.kernel.org Cc: Sergey Senozhatsky Signed-off-by: Sergey Senozhatsky Signed-off-by: Petr Mladek Signed-off-by: Sasha Levin --- kernel/printk/printk.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 5aa96098c64d3..e3dd5dcabf3e6 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -1093,7 +1093,7 @@ 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; -- 2.20.1