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[209.132.180.67]) by mx.google.com with ESMTP id 3si10993900pla.240.2019.02.11.07.26.53; Mon, 11 Feb 2019 07:27:09 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=Jr4qrUNk; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390557AbfBKP0A (ORCPT + 99 others); Mon, 11 Feb 2019 10:26:00 -0500 Received: from mail.kernel.org ([198.145.29.99]:48720 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390069AbfBKPAq (ORCPT ); Mon, 11 Feb 2019 10:00:46 -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 4EB50222A6; Mon, 11 Feb 2019 15:00:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1549897245; bh=1GC4HfULWob7YTvC/Hklvifwku4eqzrErlcpxUSl53A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Jr4qrUNkCB6GBaVJf+W3mLwhokveOG4oMIqQW3siaO1VyVo4pDabkBa/sOeGi8DqG wd8RAK+lvIuzyRaPOywNbeWM3ZBGhERdLOu8gobwPWNwk8OWYA2azKo+InuD9jAsSK lEEGLc7mDtUhWJ20AINSHCmKtqHHLDqOFCV5ugGc= 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 4.14 138/205] seq_buf: Make seq_buf_puts() null-terminate the buffer Date: Mon, 11 Feb 2019 15:18:56 +0100 Message-Id: <20190211141837.407050854@linuxfoundation.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190211141827.214852402@linuxfoundation.org> References: <20190211141827.214852402@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: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.14-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