From patchwork Thu Sep 12 10:34:52 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miles Chen X-Patchwork-Id: 11142771 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 5902813BD for ; Thu, 12 Sep 2019 10:35:06 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3697F20692 for ; Thu, 12 Sep 2019 10:35:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="g62fbqyI" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3697F20692 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=mediatek.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-mediatek-bounces+patchwork-linux-mediatek=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-ID:Date:Subject:To :From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Owner; bh=BMRQ+auTqOC3DwBDCyAlp7EEN7mqYzie8rGA/Hy7Og8=; b=g62fbqyIbjZ/mt Hhnu4tDTIontYAaK5B5ooHY0SeonrJx0kxJcCR8NVoOjJGucKBT/gzR/o+KwwvzMpT5gIMeiVGsyn xdTQvzBfjz9oP6gdPXnsq0yeePKPN4BTppV4YBuvb93xKMWP9aBZ9WqpFnioFbRZ6LS7txV4XdXsf kv0gxIHWtNFYW5TwWfRLeyvTf+vAOkVJ86dQ0vU/74QyD58oIOVYGzSGBh+m/7cPRjjHegIiAftN/ UToVJEK99YSZDZHIL/UJkteF84mMW00HaIftrWa51w1zMf9pQ4wKJxOnxClWm++6s77Sm0XI5bzKx pHja+oelaYVqmUZEHl9w==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.2 #3 (Red Hat Linux)) id 1i8MRM-0005aC-Fo; Thu, 12 Sep 2019 10:35:04 +0000 Received: from mailgw02.mediatek.com ([216.200.240.185]) by bombadil.infradead.org with esmtps (Exim 4.92.2 #3 (Red Hat Linux)) id 1i8MRK-00050e-2b for linux-mediatek@lists.infradead.org; Thu, 12 Sep 2019 10:35:03 +0000 X-UUID: 80cf54b9ca1e45ac8eff35104e021598-20190912 X-UUID: 80cf54b9ca1e45ac8eff35104e021598-20190912 Received: from mtkcas67.mediatek.inc [(172.29.193.45)] by mailgw02.mediatek.com (envelope-from ) (musrelay.mediatek.com ESMTP with TLS) with ESMTP id 1371519688; Thu, 12 Sep 2019 02:34:55 -0800 Received: from MTKMBS06N1.mediatek.inc (172.21.101.129) by MTKMBS62N1.mediatek.inc (172.29.193.41) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Thu, 12 Sep 2019 03:34:53 -0700 Received: from mtkcas07.mediatek.inc (172.21.101.84) by mtkmbs06n1.mediatek.inc (172.21.101.129) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Thu, 12 Sep 2019 18:34:51 +0800 Received: from mtksdccf07.mediatek.inc (172.21.84.99) by mtkcas07.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1395.4 via Frontend Transport; Thu, 12 Sep 2019 18:34:52 +0800 From: Miles Chen To: Ingo Molnar , Peter Zijlstra Subject: [PATCH] psi: put NULL char correctly in psi_write() Date: Thu, 12 Sep 2019 18:34:52 +0800 Message-ID: <20190912103452.13281-1-miles.chen@mediatek.com> X-Mailer: git-send-email 2.18.0 MIME-Version: 1.0 X-MTK: N X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190912_033502_129246_2ACA68AE X-CRM114-Status: UNSURE ( 8.41 ) X-CRM114-Notice: Please train this message. X-Spam-Score: 0.0 (/) X-Spam-Report: SpamAssassin version 3.4.2 on bombadil.infradead.org summary: Content analysis details: (0.0 points) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.0 SPF_PASS SPF: sender matches SPF record 0.0 UNPARSEABLE_RELAY Informational: message has unparseable relay lines X-BeenThere: linux-mediatek@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Miles Chen , linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org, wsd_upstream@mediatek.com Sender: "Linux-mediatek" Errors-To: linux-mediatek-bounces+patchwork-linux-mediatek=patchwork.kernel.org@lists.infradead.org When passing a equal or more then 32 bytes long string to psi_write(), psi_write() copies 31 bytes to its buf and overwrites buf[30] with '\0'. Which makes the input string 1 byte shorter than it should be. Fix it by copying sizeof(buf) bytes when nbytes >= sizeof(buf). This does not cause problems in normal use case like: "some 500000 10000000" or "full 500000 10000000" because they are less than 32 bytes in length. /* assuming nbytes == 35 */ char buf[32]; buf_size = min(nbytes, (sizeof(buf) - 1)); /* buf_size = 31 */ if (copy_from_user(buf, user_buf, buf_size)) return -EFAULT; buf[buf_size - 1] = '\0'; /* buf[30] = '\0' */ Before: %cd /proc/pressure/ %echo "123456789|123456789|123456789|1234" > memory [ 22.473497] nbytes=35,buf_size=31 [ 22.473775] 123456789|123456789|123456789| (print 30 chars) %sh: write error: Invalid argument %echo "123456789|123456789|123456789|1" > memory [ 64.916162] nbytes=32,buf_size=31 [ 64.916331] 123456789|123456789|123456789| (print 30 chars) %sh: write error: Invalid argument After: %cd /proc/pressure/ %echo "123456789|123456789|123456789|1234" > memory [ 254.837863] nbytes=35,buf_size=32 [ 254.838541] 123456789|123456789|123456789|1 (print 31 chars) %sh: write error: Invalid argument %echo "123456789|123456789|123456789|1" > memory [ 9965.714935] nbytes=32,buf_size=32 [ 9965.715096] 123456789|123456789|123456789|1 (print 31 chars) %sh: write error: Invalid argument Signed-off-by: Miles Chen --- kernel/sched/psi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c index 6e52b67b420e..517e3719027e 100644 --- a/kernel/sched/psi.c +++ b/kernel/sched/psi.c @@ -1198,7 +1198,7 @@ static ssize_t psi_write(struct file *file, const char __user *user_buf, if (static_branch_likely(&psi_disabled)) return -EOPNOTSUPP; - buf_size = min(nbytes, (sizeof(buf) - 1)); + buf_size = min(nbytes, sizeof(buf)); if (copy_from_user(buf, user_buf, buf_size)) return -EFAULT;