linux-kernel - [PATCH 3.19 019/177] Btrfs: fix inode eviction infinite loop after extent

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Message-Id: <20150502190120.508868186@linuxfoundation.org>
Date:	Sat,  2 May 2015 21:00:41 +0200
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Filipe Manana <fdmanana@...e.com>,
	Omar Sandoval <osandov@...ndov.com>, Chris Mason <clm@...com>
Subject: [PATCH 3.19 019/177] Btrfs: fix inode eviction infinite loop after extent_same ioctl

3.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Filipe Manana <fdmanana@...e.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@...e.com>
Reviewed-by: Omar Sandoval <osandov@...ndov.com>
Signed-off-by: Chris Mason <clm@...com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2897,6 +2897,9 @@ 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);


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