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=-9.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,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 C73C7C169C4 for ; Mon, 11 Feb 2019 15:58:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9B41721B18 for ; Mon, 11 Feb 2019 15:58:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1549900705; bh=mphhYh+4fb8gmY6A0Msp17lFA+dfA8KMqXn4KkC71+U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Oe06lDr+6KF6gsn1oeQ39qusqlhjqbzO+8cyVLVZtFhlfNZ062gfLV98FcJdGdaVI /LOxwrGXSlb0kXbUtaVB2TvCPu1qiwurEu08sAMpfom6K2SDY5LoFQOvrdeyoP5Ga9 q8uGTsxZb3Rv7nu2pF9LfsPZMvA1rPxzZ1ql14wE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730570AbfBKOdB (ORCPT ); Mon, 11 Feb 2019 09:33:01 -0500 Received: from mail.kernel.org ([198.145.29.99]:40618 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730562AbfBKOdA (ORCPT ); Mon, 11 Feb 2019 09:33:00 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.ziggo.nl [83.86.89.107]) (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 90D4020844; Mon, 11 Feb 2019 14:32:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1549895580; bh=mphhYh+4fb8gmY6A0Msp17lFA+dfA8KMqXn4KkC71+U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=R6cuikU4i1rcEyhGM9NbYrtuRT98GYLLdiXkKNLusLsWp0IDA+m0Ws0AgDpBmfrSn t9QSCwvOxMwOcEXmqfxLDSj7jsStsgXJ+aSWVt6fS+Okz7GRl772k/DVP+6zORBkt5 P7lIvdwQ5ll+zIv8lri91Fb3Rn69iZ3qs3L1OaJM= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Kees Cook , Michael Ellerman , "Steven Rostedt (VMware)" , Sasha Levin Subject: [PATCH 4.20 253/352] seq_buf: Make seq_buf_puts() null-terminate the buffer Date: Mon, 11 Feb 2019 15:18:00 +0100 Message-Id: <20190211141903.192124949@linuxfoundation.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190211141846.543045703@linuxfoundation.org> References: <20190211141846.543045703@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 4.20-stable review patch. If anyone has any objections, please let me know. ------------------ [ Upstream commit 0464ed24380905d640030d368cd84a4e4d1e15e2 ] Currently seq_buf_puts() will happily create a non null-terminated string for you in the buffer. This is particularly dangerous if the buffer is on the stack. For example: char buf[8]; char secret = "secret"; struct seq_buf s; seq_buf_init(&s, buf, sizeof(buf)); seq_buf_puts(&s, "foo"); printk("Message is %s\n", buf); Can result in: Message is fooªªªªªsecret We could require all users to memset() their buffer to zero before use. But that seems likely to be forgotten and lead to bugs. Instead we can change seq_buf_puts() to always leave the buffer in a null-terminated state. The only downside is that this makes the buffer 1 character smaller for seq_buf_puts(), but that seems like a good trade off. Link: http://lkml.kernel.org/r/20181019042109.8064-1-mpe@ellerman.id.au Acked-by: Kees Cook Signed-off-by: Michael Ellerman Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Sasha Levin --- lib/seq_buf.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/lib/seq_buf.c b/lib/seq_buf.c index 11f2ae0f9099..6aabb609dd87 100644 --- a/lib/seq_buf.c +++ b/lib/seq_buf.c @@ -144,9 +144,13 @@ int seq_buf_puts(struct seq_buf *s, const char *str) WARN_ON(s->size == 0); + /* Add 1 to len for the trailing null byte which must be there */ + len += 1; + if (seq_buf_can_fit(s, len)) { memcpy(s->buffer + s->len, str, len); - s->len += len; + /* Don't count the trailing null byte against the capacity */ + s->len += len - 1; return 0; } seq_buf_set_overflow(s); -- 2.19.1