From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753271AbbHBALX (ORCPT ); Sat, 1 Aug 2015 20:11:23 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:36039 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751838AbbHBAJt (ORCPT ); Sat, 1 Aug 2015 20:09:49 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Sasha Levin" , "Al Viro" , "Linus Torvalds" Date: Sun, 02 Aug 2015 01:02:37 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 111/164] vfs: read file_handle only once in handle_to_path In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.249 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.70-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Sasha Levin commit 161f873b89136eb1e69477c847d5a5033239d9ba upstream. We used to read file_handle twice. Once to get the amount of extra bytes, and once to fetch the entire structure. This may be problematic since we do size verifications only after the first read, so if the number of extra bytes changes in userspace between the first and second calls, we'll have an incoherent view of file_handle. Instead, read the constant size once, and copy that over to the final structure without having to re-read it again. Signed-off-by: Sasha Levin Cc: Al Viro Signed-off-by: Linus Torvalds Signed-off-by: Ben Hutchings --- fs/fhandle.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- a/fs/fhandle.c +++ b/fs/fhandle.c @@ -196,8 +196,9 @@ static int handle_to_path(int mountdirfd goto out_err; } /* copy the full handle */ - if (copy_from_user(handle, ufh, - sizeof(struct file_handle) + + *handle = f_handle; + if (copy_from_user(&handle->f_handle, + &ufh->f_handle, f_handle.handle_bytes)) { retval = -EFAULT; goto out_handle;