From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967389AbaFQVzz (ORCPT ); Tue, 17 Jun 2014 17:55:55 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:54999 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965818AbaFQVxM (ORCPT ); Tue, 17 Jun 2014 17:53:12 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Tejun Heo , Greg Kroah-Hartman , Kamal Mostafa Subject: [PATCH 3.13 141/212] sysfs: make sure read buffer is zeroed Date: Tue, 17 Jun 2014 14:43:55 -0700 Message-Id: <1403041506-13646-142-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1403041506-13646-1-git-send-email-kamal@canonical.com> References: <1403041506-13646-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.13 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.13.11.4 -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 Signed-off-by: Kamal Mostafa --- fs/sysfs/file.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c index 35e7d08..ea3e7e2 100644 --- a/fs/sysfs/file.c +++ b/fs/sysfs/file.c @@ -94,12 +94,13 @@ static int sysfs_seq_show(struct seq_file *sf, void *v) char *buf; ssize_t count; - /* 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); /* * Need @of->sd for attr and ops, its parent for kobj. @of->mutex -- 1.9.1