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[209.132.180.67]) by mx.google.com with ESMTP id t4si1596562ejd.328.2019.09.24.14.28.23; Tue, 24 Sep 2019 14:28:46 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=P06yKy7A; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729093AbfIVTb2 (ORCPT + 99 others); Sun, 22 Sep 2019 15:31:28 -0400 Received: from mail.kernel.org ([198.145.29.99]:45778 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2391802AbfIVSsu (ORCPT ); Sun, 22 Sep 2019 14:48:50 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (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 AD41321D71; Sun, 22 Sep 2019 18:48:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1569178129; bh=/F0eqdyJKABuAv6cUV90z+rRaHqrSXh+R+pUYfvNIeM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=P06yKy7AMcLsqCYwNzDXEDODLsuVeSam+In8JhOhMNdug2ZhJcu7f2vd7fpIqSU8c 4Wm8ICy2PZ48/vgevmDxSyhAaoTCd5q19F5x80mYsG8VOBndh66u2Y7aWp0hh4zKvK PUx1Ev6aw5yMS4Nb9V4dbWwHYKF4B7f86sHG53QE= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Miles Chen , linux-mediatek@lists.infradead.org, wsd_upstream@mediatek.com, Linus Torvalds , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Sasha Levin Subject: [PATCH AUTOSEL 5.3 182/203] sched/psi: Correct overly pessimistic size calculation Date: Sun, 22 Sep 2019 14:43:28 -0400 Message-Id: <20190922184350.30563-182-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190922184350.30563-1-sashal@kernel.org> References: <20190922184350.30563-1-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: Miles Chen [ Upstream commit 4adcdcea717cb2d8436bef00dd689aa5bc76f11b ] 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 Also remove the superfluous parentheses. Signed-off-by: Miles Chen Cc: Cc: Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: https://lkml.kernel.org/r/20190912103452.13281-1-miles.chen@mediatek.com Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin --- 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 6e52b67b420e7..517e3719027e6 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; -- 2.20.1