Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756128AbaFEALy (ORCPT ); Wed, 4 Jun 2014 20:11:54 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:40304 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753359AbaFDXWs (ORCPT ); Wed, 4 Jun 2014 19:22:48 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tejun Heo , Ron Subject: [PATCH 3.14 173/228] sysfs: make sure read buffer is zeroed Date: Wed, 4 Jun 2014 16:23:22 -0700 Message-Id: <20140604232353.580003687@linuxfoundation.org> X-Mailer: git-send-email 1.9.0 In-Reply-To: <20140604232347.966798903@linuxfoundation.org> References: <20140604232347.966798903@linuxfoundation.org> User-Agent: quilt/0.63-1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tejun Heo commit f5c16f29bf5e57ba4051fc7785ba7f035f798c71 upstream. 13c589d5b0ac ("sysfs: use seq_file when reading regular files") switched sysfs from custom read implementation to seq_file to enable later transition to kernfs. After the change, the buffer passed to ->show() is acquired through seq_get_buf(); unfortunately, this introduces a subtle behavior change. Before the commit, the buffer passed to ->show() was always zero as it was allocated using get_zeroed_page(). Because seq_file doesn't clear buffers on allocation and neither does seq_get_buf(), after the commit, depending on the behavior of ->show(), we may end up exposing uninitialized data to userland thus possibly altering userland visible behavior and leaking information. Fix it by explicitly clearing the buffer. Signed-off-by: Tejun Heo Reported-by: Ron Fixes: 13c589d5b0ac ("sysfs: use seq_file when reading regular files") Signed-off-by: Greg Kroah-Hartman --- fs/sysfs/file.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/fs/sysfs/file.c +++ b/fs/sysfs/file.c @@ -47,12 +47,13 @@ static int sysfs_kf_seq_show(struct seq_ ssize_t count; char *buf; - /* acquire buffer and ensure that it's >= PAGE_SIZE */ + /* acquire buffer and ensure that it's >= PAGE_SIZE and clear */ count = seq_get_buf(sf, &buf); if (count < PAGE_SIZE) { seq_commit(sf, -1); return 0; } + memset(buf, 0, PAGE_SIZE); /* * Invoke show(). Control may reach here via seq file lseek even -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/