[PATCH 3.14 09/92] Btrfs: fix inode eviction infinite loop after extent_same ioctl

Greg Kroah-Hartman
2015-05-02T19:42:24Z

From: Filipe Manana <fdmanana@suse.com>

commit 113e8283869b9855c8b999796aadd506bbac155f upstream.

If we pass a length of 0 to the extent_same ioctl, we end up locking an
extent range with a start offset greater then its end offset (if the
destination file's offset is greater than zero). This results in a warning
from extent_io.c:insert_state through the following call chain:

btrfs_extent_same()
btrfs_double_lock()
lock_extent_range()
lock_extent(inode->io_tree, offset, offset + len - 1)
lock_extent_bits()
__set_extent_bit()
insert_state()
--> WARN_ON(end < start)

This leads to an infinite loop when evicting the inode. This is the same
problem that my previous patch titled
"Btrfs: fix inode eviction infinite loop after cloning into it" addressed
but for the extent_same ioctl instead of the clone ioctl.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Omar Sandoval <osandov@osandov.com>
Signed-off-by: Chris Mason <clm@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/btrfs/ioctl.c | 3 +++
1 file changed, 3 insertions(+)

--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2708,6 +2708,9 @@ static int btrfs_extent_same(struct inod
if (src == dst)
return -EINVAL;

+ if (len == 0)
+ return 0;
+
btrfs_double_lock(src, loff, dst, dst_loff, len);

ret = extent_same_check_offsets(src, loff, len);