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 X-Spam-Level: X-Spam-Status: No, score=-9.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 14EFFC432C0 for ; Wed, 20 Nov 2019 08:39:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CECA621852 for ; Wed, 20 Nov 2019 08:39:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="dkONEBDm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727834AbfKTIjM (ORCPT ); Wed, 20 Nov 2019 03:39:12 -0500 Received: from mail-pg1-f178.google.com ([209.85.215.178]:42945 "EHLO mail-pg1-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726687AbfKTIjL (ORCPT ); Wed, 20 Nov 2019 03:39:11 -0500 Received: by mail-pg1-f178.google.com with SMTP id q17so12971239pgt.9 for ; Wed, 20 Nov 2019 00:39:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=xAGvmCTTbiFZa1QD8p7bE0Fit3+vMtBk+hQsXBR0Omg=; b=dkONEBDmB99HrgTrs18mo1W17bGWN23AI7/JWAWCW45D7gxAp6Rd4BlrH7PXHwzojP iYncy4ZE5PEaE0kuTNaLWBIbaCn6zRJvoXKooC1v+VmTTOGYzP5MFgDwvrPgQbADbM5l mTwuZwu/IaslxTW+JpEJ7JoINFcMmzzsB2hh/k/3dklmmPvoWQhtDhcpd6RZPQHg57V5 K6Fm6ZDjMerIb9WlAVhcYTrgD4ypZUfQrt+XOn4Nl18vE3MkYEl0GrK+1tpu0/O4jtDp fJuvizu9c1xjZlgbXVRP2UmeqiOuy2jq/GN21JsSTSOwnLDEWJhnjnI5f6RKxKXge/Zj /+hA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=xAGvmCTTbiFZa1QD8p7bE0Fit3+vMtBk+hQsXBR0Omg=; b=oZT2EaTxGE5Hhi73Qo0iYHsWwTj729PmeSEtyYOSYscH05zCPz5yO6NO5wiP82ZXvB jZ9jYu59QbBp9tM3kus0dsN0mDDQPo9QD7S8iylvbrd64Et/+uX1fTvmekyfGDUCpmkr FLcXXJRFEHfoOvcJCMcfDQw8YPD0ZBZ9kDNsBjxJA//Ju575BBz63ULSkDtu4g420Y3J iKn7T0xsAa7Td3ANPo8Mlu4tia5z6IMKghi5TRqklHPU3DDPu4Gto9xPWg0zmYFhLMwk QeqY+K5GAzzkPeX/npSYu93QrCipNrm1WFp4m1ActaFNI8244Lvud4kNRh0bSB2WsGbG IWkQ== X-Gm-Message-State: APjAAAX8iEZnqtMq1j151WSWSOkPaBhHD7EPFxBnozWh4DPYJLzKGqF4 cgwNAud2zKYQUDmkzsGaC37fDq1O+y3PmQ== X-Google-Smtp-Source: APXvYqwBsw7kaGOfL/uBa86iygBtGTI6DdSDOqhNRyNVgK3LMTYJQV1KYybh5iaG0iFHO4g+r1l1Ng== X-Received: by 2002:a62:7f93:: with SMTP id a141mr2592526pfd.82.1574239150890; Wed, 20 Nov 2019 00:39:10 -0800 (PST) Received: from dhcp-12-139.nay.redhat.com ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id z11sm31300917pfg.117.2019.11.20.00.39.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 Nov 2019 00:39:10 -0800 (PST) From: Hangbin Liu To: netdev@vger.kernel.org Cc: Jiri Benc , "David S . Miller" , Eric Dumazet , Hangbin Liu Subject: [PATCHv2 net-next] tcp: warn if offset reach the maxlen limit when using snprintf Date: Wed, 20 Nov 2019 16:38:08 +0800 Message-Id: <20191120083808.16382-1-liuhangbin@gmail.com> X-Mailer: git-send-email 2.19.2 In-Reply-To: <20191114102831.23753-1-liuhangbin@gmail.com> References: <20191114102831.23753-1-liuhangbin@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org snprintf returns the number of chars that would be written, not number of chars that were actually written. As such, 'offs' may get larger than 'tbl.maxlen', causing the 'tbl.maxlen - offs' being < 0, and since the parameter is size_t, it would overflow. Since using scnprintf may hide the limit error, while the buffer is still enough now, let's just add a WARN_ON_ONCE in case it reach the limit in future. v2: Use WARN_ON_ONCE as Jiri and Eric suggested. Suggested-by: Jiri Benc Signed-off-by: Hangbin Liu --- net/ipv4/sysctl_net_ipv4.c | 4 ++++ net/ipv4/tcp_cong.c | 6 ++++++ net/ipv4/tcp_ulp.c | 3 +++ 3 files changed, 13 insertions(+) diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c index 59ded25acd04..c9eaf924df63 100644 --- a/net/ipv4/sysctl_net_ipv4.c +++ b/net/ipv4/sysctl_net_ipv4.c @@ -340,6 +340,10 @@ static int proc_tcp_fastopen_key(struct ctl_table *table, int write, user_key[i * 4 + 1], user_key[i * 4 + 2], user_key[i * 4 + 3]); + + if (WARN_ON_ONCE(off >= tbl.maxlen - 1)) + break; + if (i + 1 < n_keys) off += snprintf(tbl.data + off, tbl.maxlen - off, ","); } diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c index c445a81d144e..3737ec096650 100644 --- a/net/ipv4/tcp_cong.c +++ b/net/ipv4/tcp_cong.c @@ -256,6 +256,9 @@ void tcp_get_available_congestion_control(char *buf, size_t maxlen) offs += snprintf(buf + offs, maxlen - offs, "%s%s", offs == 0 ? "" : " ", ca->name); + + if (WARN_ON_ONCE(offs >= maxlen)) + break; } rcu_read_unlock(); } @@ -285,6 +288,9 @@ void tcp_get_allowed_congestion_control(char *buf, size_t maxlen) offs += snprintf(buf + offs, maxlen - offs, "%s%s", offs == 0 ? "" : " ", ca->name); + + if (WARN_ON_ONCE(offs >= maxlen)) + break; } rcu_read_unlock(); } diff --git a/net/ipv4/tcp_ulp.c b/net/ipv4/tcp_ulp.c index 4849edb62d52..12ab5db2b71c 100644 --- a/net/ipv4/tcp_ulp.c +++ b/net/ipv4/tcp_ulp.c @@ -92,6 +92,9 @@ void tcp_get_available_ulp(char *buf, size_t maxlen) offs += snprintf(buf + offs, maxlen - offs, "%s%s", offs == 0 ? "" : " ", ulp_ops->name); + + if (WARN_ON_ONCE(offs >= maxlen)) + break; } rcu_read_unlock(); } -- 2.19.2