From patchwork Tue Sep 29 11:00:05 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 290775 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=-13.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=unavailable 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 02714C4727C for ; Tue, 29 Sep 2020 12:38:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A809920789 for ; Tue, 29 Sep 2020 12:38:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601383082; bh=AVpRSkgj0eO6IkQtoEcXFT1DLNyNXuMgutww47Zi4pk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=L6VhG+ctW3PZm/Re+RtORz8XcktqtCrwQHrQQbgv+W8ZbhAqcBo3/mYMeMVymYqQ/ KgPmOOZDAVG//rqGvOQhGwdn6NSUAMCaTo5nEquOYz5iPMsPuTTJORD8VHX8I0xjv/ uJUfNOq+Virpjq1myPy4iW3qI4zYVTn4dhZGc5ds= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733047AbgI2Mhw (ORCPT ); Tue, 29 Sep 2020 08:37:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:35550 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728535AbgI2LR5 (ORCPT ); Tue, 29 Sep 2020 07:17:57 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 41B33221E7; Tue, 29 Sep 2020 11:17:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601378276; bh=AVpRSkgj0eO6IkQtoEcXFT1DLNyNXuMgutww47Zi4pk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YRnL3ZjzjxMmmk6uByosXRdzk2Z/NyZeAwKJDbB1WFUljQ+Y05JEe0Xe+AIeeYu/2 JgM3n2axsVunG3+1HHRPS+3JNHKGRDD8gDwh5bG74BnZoYDpuqNhNaSBC6J3WU2JCF 2zBiV9kQVeCxWec73Wv2HwPru9CIpnlqsbQYUzk8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Christophe JAILLET , Chuck Lever , Sasha Levin Subject: [PATCH 4.14 093/166] SUNRPC: Fix a potential buffer overflow in svc_print_xprts() Date: Tue, 29 Sep 2020 13:00:05 +0200 Message-Id: <20200929105939.864115668@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200929105935.184737111@linuxfoundation.org> References: <20200929105935.184737111@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Christophe JAILLET [ Upstream commit b25b60d7bfb02a74bc3c2d998e09aab159df8059 ] 'maxlen' is the total size of the destination buffer. There is only one caller and this value is 256. When we compute the size already used and what we would like to add in the buffer, the trailling NULL character is not taken into account. However, this trailling character will be added by the 'strcat' once we have checked that we have enough place. So, there is a off-by-one issue and 1 byte of the stack could be erroneously overwridden. Take into account the trailling NULL, when checking if there is enough place in the destination buffer. While at it, also replace a 'sprintf' by a safer 'snprintf', check for output truncation and avoid a superfluous 'strlen'. Fixes: dc9a16e49dbba ("svc: Add /proc/sys/sunrpc/transport files") Signed-off-by: Christophe JAILLET [ cel: very minor fix to documenting comment Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin --- net/sunrpc/svc_xprt.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c index 7e5f849b44cdb..b293827b2a583 100644 --- a/net/sunrpc/svc_xprt.c +++ b/net/sunrpc/svc_xprt.c @@ -103,8 +103,17 @@ void svc_unreg_xprt_class(struct svc_xprt_class *xcl) } EXPORT_SYMBOL_GPL(svc_unreg_xprt_class); -/* - * Format the transport list for printing +/** + * svc_print_xprts - Format the transport list for printing + * @buf: target buffer for formatted address + * @maxlen: length of target buffer + * + * Fills in @buf with a string containing a list of transport names, each name + * terminated with '\n'. If the buffer is too small, some entries may be + * missing, but it is guaranteed that all lines in the output buffer are + * complete. + * + * Returns positive length of the filled-in string. */ int svc_print_xprts(char *buf, int maxlen) { @@ -117,9 +126,9 @@ int svc_print_xprts(char *buf, int maxlen) list_for_each_entry(xcl, &svc_xprt_class_list, xcl_list) { int slen; - sprintf(tmpstr, "%s %d\n", xcl->xcl_name, xcl->xcl_max_payload); - slen = strlen(tmpstr); - if (len + slen > maxlen) + slen = snprintf(tmpstr, sizeof(tmpstr), "%s %d\n", + xcl->xcl_name, xcl->xcl_max_payload); + if (slen >= sizeof(tmpstr) || len + slen >= maxlen) break; len += slen; strcat(buf, tmpstr);