From 41b34accb265e3a20211a7a8ef3625678f1c6ec7 Mon Sep 17 00:00:00 2001 From: Luis de Bethencourt Date: Wed, 30 Mar 2016 23:18:14 +0100 Subject: [PATCH] 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 Suggested-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/super.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index bdca79ce..fe03efb 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -2100,7 +2100,11 @@ 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); -- 2.7.4