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Date: Wed, 30 Mar 2016 21:53:39 +0100 From: Luis de Bethencourt <luisbg@....samsung.com> To: linux-kernel@...r.kernel.org Cc: clm@...com, jbacik@...com, dsterba@...e.com, linux-btrfs@...r.kernel.org, Luis de Bethencourt <luisbg@....samsung.com> Subject: [PATCH 2/2] btrfs: avoid overflowing f_bfree 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 <luisbg@....samsung.com> Suggested-by: David Sterba <dsterba@...e.com> --- 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
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