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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BE301ECAAD3 for ; Mon, 5 Sep 2022 10:52:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237696AbiIEKwB (ORCPT ); Mon, 5 Sep 2022 06:52:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34130 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230073AbiIEKvy (ORCPT ); Mon, 5 Sep 2022 06:51:54 -0400 Received: from gnuweeb.org (gnuweeb.org [51.81.211.47]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 57AC14E625 for ; Mon, 5 Sep 2022 03:51:52 -0700 (PDT) Received: from localhost.localdomain (unknown [182.2.42.181]) by gnuweeb.org (Postfix) with ESMTPSA id 4D71C804D1; Mon, 5 Sep 2022 10:51:47 +0000 (UTC) X-GW-Data: lPqxHiMPbJw1wb7CM9QUryAGzr0yq5atzVDdxTR0iA== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=gnuweeb.org; s=default; t=1662375111; bh=c9zeHPFx76P0oLkPbZmlW5hML9U+k3vaPD6cjMJ/lpY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=nCir+0wH/YIfJUt8VqCmGvtKYo5+Mny+OxFeEHP3YszeSd5OgbwXTfyJ7HwbI5ouc RsX0MXSkY1w0ZdwQXdPwc0HMKg4+J4UWYeRcZjR7qk5x87WQUNmdGjM/lqLCfsJ9Rd AO0RUOGOfNmM8felbyyR+n7g7n4nTfK/Fyx98GpBK5GcD6Xma1Ak2r7VDtrzpu1s/j VI6mI+p7U+wAVsXJtIVWIiaEldFWqaoBlHM/P2ZHeKiyXjQZzXS/FEXJjlCS7QwALV WHUqHMcZS5vK/fAy0kpph/95q45xWJwXKxlKzMuUOi7ELUP2a2dICM5wwnkZb4e3+i scDzCTRRT6uhg== From: Ammar Faizi To: Oscar Salvador Cc: Andrew Morton , Linux Kernel Mailing List , Linux Memory Management Mailing List , Michal Hocko , Vlastimil Babka , Eric Dumazet , Waiman Long , Suren Baghdasaryan , Marco Elver , Andrey Konovalov , Alexander Potapenko Subject: Re: [PATCH v2 3/3] mm,page_owner: Filter out stacks by a threshold counter Date: Mon, 5 Sep 2022 17:51:37 +0700 Message-Id: <573c4049045a5ff342ff9998c69dfae7-ammarfaizi2@gnuweeb.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220905031012.4450-4-osalvador@suse.de> References: <20220905031012.4450-1-osalvador@suse.de>, <20220905031012.4450-4-osalvador@suse.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 5 Sep 2022 05:10:12 +0200, Oscar Salvador wrote: > +static int page_owner_threshold_show(struct seq_file *p, void *v) > +{ > + seq_printf(p, "%lu\n", threshold); Remove a slipped leading 0x20 space here (before seq_printf()). > + return 0; > +} > + > +static ssize_t write_page_owner_threshold(struct file *file, const char __user *buf, > + size_t count, loff_t *pos) > +{ > + char *kbuf; > + int ret = 0; > + > + count = min_t(size_t, count, PAGE_SIZE); > + kbuf = kmalloc(count, GFP_KERNEL); > + if (!kbuf) > + return -ENOMEM; > + > + if (copy_from_user(kbuf, buf, count)) { > + ret = -EFAULT; > + goto out; > + } > + > + kbuf[count - 1] = '\0'; > + > + ret = kstrtoul(kbuf, 10, &threshold); > + > +out: > + kfree(kbuf); > + return ret ? ret : count; > +} Still the same comment on this, kmalloc() is not really needed here. Capping the size to PAGE_SIZE (usually 4K) is too big. `unsinged long` is 64-bit at most, this means the max val is 18446744073709551615 (20 chars). The lifetime of @kbuf is very short as well, using a stack allocated array of chars is fine? Untested: static ssize_t write_page_owner_threshold(struct file *file, const char __user *buf, size_t count, loff_t *pos) { char kbuf[21]; int ret; count = min_t(size_t, count, sizeof(kbuf)); if (copy_from_user(kbuf, buf, count)) return -EFAULT; kbuf[count - 1] = '\0'; ret = kstrtoul(kbuf, 10, &threshold); return ret ? ret : count; } -- Ammar Faizi