From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sasha Levin Subject: [PATCH v2] vfs: read file_handle only once in handle_to_path Date: Wed, 28 Jan 2015 15:30:43 -0500 Message-ID: <1422477048-4550-1-git-send-email-sasha.levin@oracle.com> Cc: Sasha Levin , Alexander Viro , linux-fsdevel@vger.kernel.org To: linux-kernel@vger.kernel.org Return-path: Received: from userp1040.oracle.com ([156.151.31.81]:42290 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759636AbbA1UbB (ORCPT ); Wed, 28 Jan 2015 15:31:01 -0500 Sender: linux-fsdevel-owner@vger.kernel.org List-ID: 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 --- Change in v2: - Use the f_handle pointer rather than size of struct fs/fhandle.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/fs/fhandle.c b/fs/fhandle.c index 999ff5c..d59712d 100644 --- a/fs/fhandle.c +++ b/fs/fhandle.c @@ -195,8 +195,9 @@ static int handle_to_path(int mountdirfd, struct file_handle __user *ufh, 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; -- 1.7.10.4