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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6765AC433EF for ; Tue, 8 Feb 2022 00:06:09 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E66706B007B; Mon, 7 Feb 2022 19:06:08 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E16AB6B007E; Mon, 7 Feb 2022 19:06:08 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C401B6B007B; Mon, 7 Feb 2022 19:06:08 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0080.hostedemail.com [216.40.44.80]) by kanga.kvack.org (Postfix) with ESMTP id B35286B0075 for ; Mon, 7 Feb 2022 19:06:08 -0500 (EST) Received: from smtpin10.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 7E2BE181DFAAA for ; Tue, 8 Feb 2022 00:06:08 +0000 (UTC) X-FDA: 79117670016.10.FA9D84F Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf20.hostedemail.com (Postfix) with ESMTP id 252D11C0002 for ; Tue, 8 Feb 2022 00:06:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1644278767; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ARpUf0IirgM+NjOFiLN9kgiVvRtzmNfHi46LW66TM0Q=; b=JuhQbyQs1Y3NcH5AJhgOfll2Ad0HHxebheRyNdQzKJ+HB9mWWbuNXToCgHJFMSVxcQ7ZRX ob5Pjbby+UFTpT/CgCu8NDc+7OyiXVIz9F73iRjLLs8+wrOoeT4xm2spGN9+G84V1gmw9/ xqF8Zesb2F0o4J7KUAUBT68gQ2u+PA4= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-608-UwoFt0qcNrqvMjJbZo_NBA-1; Mon, 07 Feb 2022 19:06:04 -0500 X-MC-Unique: UwoFt0qcNrqvMjJbZo_NBA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7BBDE100C660; Tue, 8 Feb 2022 00:06:01 +0000 (UTC) Received: from llong.com (unknown [10.22.32.15]) by smtp.corp.redhat.com (Postfix) with ESMTP id D29C85C2EF; Tue, 8 Feb 2022 00:05:59 +0000 (UTC) From: Waiman Long To: Johannes Weiner , Michal Hocko , Vladimir Davydov , Andrew Morton , Petr Mladek , Steven Rostedt , Sergey Senozhatsky , Andy Shevchenko , Rasmus Villemoes Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Ira Weiny , Mike Rapoport , David Rientjes , Roman Gushchin , Rafael Aquini , Waiman Long , Mike Rapoport Subject: [PATCH v5 2/4] mm/page_owner: Use scnprintf() to avoid excessive buffer overrun check Date: Mon, 7 Feb 2022 19:05:30 -0500 Message-Id: <20220208000532.1054311-3-longman@redhat.com> In-Reply-To: <20220208000532.1054311-1-longman@redhat.com> References: <20220208000532.1054311-1-longman@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Rspamd-Queue-Id: 252D11C0002 Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=JuhQbyQs; spf=none (imf20.hostedemail.com: domain of longman@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=longman@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-Stat-Signature: 6jgycfjj6jrepf5xzi14xzy8jg8brc5j X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1644278767-959572 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: The snprintf() function can return a length greater than the given input size. That will require a check for buffer overrun after each invocation of snprintf(). scnprintf(), on the other hand, will never return a greater length. By using scnprintf() in selected places, we can avoid some buffer overrun checks except after stack_depot_snprint() and after the last snprintf(). Signed-off-by: Waiman Long Acked-by: David Rientjes Reviewed-by: Sergey Senozhatsky Acked-by: Mike Rapoport --- mm/page_owner.c | 14 +++----------- 1 file changed, 3 insertions(+), 11 deletions(-) diff --git a/mm/page_owner.c b/mm/page_owner.c index 99e360df9465..28dac73e0542 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -338,19 +338,16 @@ print_page_owner(char __user *buf, size_t count, un= signed long pfn, if (!kbuf) return -ENOMEM; =20 - ret =3D snprintf(kbuf, count, + ret =3D scnprintf(kbuf, count, "Page allocated via order %u, mask %#x(%pGg), pid %d, ts %llu ns, fre= e_ts %llu ns\n", page_owner->order, page_owner->gfp_mask, &page_owner->gfp_mask, page_owner->pid, page_owner->ts_nsec, page_owner->free_ts_nsec); =20 - if (ret >=3D count) - goto err; - /* Print information relevant to grouping pages by mobility */ pageblock_mt =3D get_pageblock_migratetype(page); page_mt =3D gfp_migratetype(page_owner->gfp_mask); - ret +=3D snprintf(kbuf + ret, count - ret, + ret +=3D scnprintf(kbuf + ret, count - ret, "PFN %lu type %s Block %lu type %s Flags %pGp\n", pfn, migratetype_names[page_mt], @@ -358,19 +355,14 @@ print_page_owner(char __user *buf, size_t count, un= signed long pfn, migratetype_names[pageblock_mt], &page->flags); =20 - if (ret >=3D count) - goto err; - ret +=3D stack_depot_snprint(handle, kbuf + ret, count - ret, 0); if (ret >=3D count) goto err; =20 if (page_owner->last_migrate_reason !=3D -1) { - ret +=3D snprintf(kbuf + ret, count - ret, + ret +=3D scnprintf(kbuf + ret, count - ret, "Page has been migrated, last migrate reason: %s\n", migrate_reason_names[page_owner->last_migrate_reason]); - if (ret >=3D count) - goto err; } =20 ret +=3D snprintf(kbuf + ret, count - ret, "\n"); --=20 2.27.0