Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754327AbcC3Uxx (ORCPT ); Wed, 30 Mar 2016 16:53:53 -0400 Received: from lists.s-osg.org ([54.187.51.154]:59318 "EHLO lists.s-osg.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753536AbcC3Uxv (ORCPT ); Wed, 30 Mar 2016 16:53:51 -0400 From: Luis de Bethencourt To: linux-kernel@vger.kernel.org Cc: clm@fb.com, jbacik@fb.com, dsterba@suse.com, linux-btrfs@vger.kernel.org, Luis de Bethencourt Subject: [PATCH 2/2] btrfs: avoid overflowing f_bfree Date: Wed, 30 Mar 2016 21:53:39 +0100 Message-Id: <1459371219-1815-2-git-send-email-luisbg@osg.samsung.com> X-Mailer: git-send-email 2.5.1 In-Reply-To: <1459371219-1815-1-git-send-email-luisbg@osg.samsung.com> References: <1459371219-1815-1-git-send-email-luisbg@osg.samsung.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 951 Lines: 27 Since mixed block groups accounting isn't byte-accurate and f_bree is an unsigned integer, it could overflow. Avoid this. Signed-off-by: Luis de Bethencourt Suggested-by: David Sterba --- fs/btrfs/super.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index bdca79c..93376d0 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -2101,6 +2101,11 @@ static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf) /* Account global block reserve as used, it's in logical size already */ spin_lock(&block_rsv->lock); buf->f_bfree -= block_rsv->size >> bits; + /* Mixed block groups accounting is not byte-accurate, avoid overflow */ + if (buf->f_bfree >= block_rsv->size >> bits) + buf->f_bfree -= block_rsv->size >> bits; + else + buf->f_bfree = 0; spin_unlock(&block_rsv->lock); buf->f_bavail = div_u64(total_free_data, factor); -- 2.5.3