From patchwork Wed Feb 2 20:30:34 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 12733456 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 D3A28C433EF for ; Wed, 2 Feb 2022 20:33:57 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 63D836B02C0; Wed, 2 Feb 2022 15:33:57 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 5ECF26B02C1; Wed, 2 Feb 2022 15:33:57 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 48DD56B02C3; Wed, 2 Feb 2022 15:33:57 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0051.hostedemail.com [216.40.44.51]) by kanga.kvack.org (Postfix) with ESMTP id 3992F6B02C0 for ; Wed, 2 Feb 2022 15:33:57 -0500 (EST) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id E2661182888C6 for ; Wed, 2 Feb 2022 20:33:56 +0000 (UTC) X-FDA: 79098991272.13.35B1DB3 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf26.hostedemail.com (Postfix) with ESMTP id 8A0BC140003 for ; Wed, 2 Feb 2022 20:33:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1643834036; 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=aswR5jLflKHAA/2KWO7s8HDPhJp/8ybDJLjB9qtlMrw=; b=MdeCq5j1htWObePAKRcyAaAJBSPWZrfBjH+gkdGjaq0+scBNHLQJIyA0wk5e+WKPB6Bp/N rAT88O9qRQs3zTJwqubIEvPvEIW5O1nsqts4WJtN1LapVMj/9EWhcTVwpte4gy+9X+vszO WtGaGK5W3P0ipfNLbwjFtIykdzN+8VE= 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-544-_oSbZEydPAiJCv_mdPNglg-1; Wed, 02 Feb 2022 15:33:54 -0500 X-MC-Unique: _oSbZEydPAiJCv_mdPNglg-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B5EA61091DB5; Wed, 2 Feb 2022 20:33:52 +0000 (UTC) Received: from llong.com (unknown [10.22.34.202]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0A30D12E2D; Wed, 2 Feb 2022 20:33:19 +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 Subject: [PATCH v4 2/4] mm/page_owner: Use scnprintf() to avoid excessive buffer overrun check Date: Wed, 2 Feb 2022 15:30:34 -0500 Message-Id: <20220202203036.744010-3-longman@redhat.com> In-Reply-To: <20220131192308.608837-5-longman@redhat.com> References: <20220131192308.608837-5-longman@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 8A0BC140003 X-Stat-Signature: fyjydcxqua8szx7nh46ztokh5xxin6uz X-Rspam-User: nil Authentication-Results: imf26.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=MdeCq5j1; spf=none (imf26.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-HE-Tag: 1643834036-373897 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 --- 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, unsigned long pfn, if (!kbuf) return -ENOMEM; - ret = snprintf(kbuf, count, + ret = scnprintf(kbuf, count, "Page allocated via order %u, mask %#x(%pGg), pid %d, ts %llu ns, free_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); - if (ret >= count) - goto err; - /* Print information relevant to grouping pages by mobility */ pageblock_mt = get_pageblock_migratetype(page); page_mt = gfp_migratetype(page_owner->gfp_mask); - ret += snprintf(kbuf + ret, count - ret, + ret += 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, unsigned long pfn, migratetype_names[pageblock_mt], &page->flags); - if (ret >= count) - goto err; - ret += stack_depot_snprint(handle, kbuf + ret, count - ret, 0); if (ret >= count) goto err; if (page_owner->last_migrate_reason != -1) { - ret += snprintf(kbuf + ret, count - ret, + ret += scnprintf(kbuf + ret, count - ret, "Page has been migrated, last migrate reason: %s\n", migrate_reason_names[page_owner->last_migrate_reason]); - if (ret >= count) - goto err; } ret += snprintf(kbuf + ret, count - ret, "\n");