From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:32858 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964830AbeGAQRj (ORCPT ); Sun, 1 Jul 2018 12:17:39 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Omar Sandoval , Nikolay Borisov , David Sterba Subject: [PATCH 4.4 061/105] Btrfs: fix clone vs chattr NODATASUM race Date: Sun, 1 Jul 2018 18:02:11 +0200 Message-Id: <20180701153153.923725936@linuxfoundation.org> In-Reply-To: <20180701153149.382300170@linuxfoundation.org> References: <20180701153149.382300170@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Omar Sandoval commit b5c40d598f5408bd0ca22dfffa82f03cd9433f23 upstream. In btrfs_clone_files(), we must check the NODATASUM flag while the inodes are locked. Otherwise, it's possible that btrfs_ioctl_setflags() will change the flags after we check and we can end up with a party checksummed file. The race window is only a few instructions in size, between the if and the locks which is: 3834 if (S_ISDIR(src->i_mode) || S_ISDIR(inode->i_mode)) 3835 return -EISDIR; where the setflags must be run and toggle the NODATASUM flag (provided the file size is 0). The clone will block on the inode lock, segflags takes the inode lock, changes flags, releases log and clone continues. Not impossible but still needs a lot of bad luck to hit unintentionally. Fixes: 0e7b824c4ef9 ("Btrfs: don't make a file partly checksummed through file clone") CC: stable@vger.kernel.org # 4.4+ Signed-off-by: Omar Sandoval Reviewed-by: Nikolay Borisov Reviewed-by: David Sterba [ update changelog ] Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman [ adjusted for 4.4 ] Signed-off-by: Nikolay Borisov --- fs/btrfs/ioctl.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -3923,11 +3923,6 @@ static noinline long btrfs_ioctl_clone(s if (!(src_file.file->f_mode & FMODE_READ)) goto out_fput; - /* don't make the dst file partly checksummed */ - if ((BTRFS_I(src)->flags & BTRFS_INODE_NODATASUM) != - (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) - goto out_fput; - ret = -EISDIR; if (S_ISDIR(src->i_mode) || S_ISDIR(inode->i_mode)) goto out_fput; @@ -3942,6 +3937,13 @@ static noinline long btrfs_ioctl_clone(s mutex_lock(&src->i_mutex); } + /* don't make the dst file partly checksummed */ + if ((BTRFS_I(src)->flags & BTRFS_INODE_NODATASUM) != + (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) { + ret = -EINVAL; + goto out_unlock; + } + /* determine range to clone */ ret = -EINVAL; if (off + len > src->i_size || off + len < off)