linux-kernel - [PATCH 3.12 009/142] Btrfs: fix inode eviction infinite loop after extent

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Date:	Sat, 16 May 2015 09:36:09 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Filipe Manana <fdmanana@...e.com>,
	Chris Mason <clm@...com>, Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 009/142] Btrfs: fix inode eviction infinite loop after extent_same ioctl

From: Filipe Manana <fdmanana@...e.com>

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

===============

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: Jiri Slaby <jslaby@...e.cz>
---
 fs/btrfs/ioctl.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 3cf8a7b671cb..d43cd15c3097 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2671,6 +2671,9 @@ static int btrfs_extent_same(struct inode *src, u64 loff, u64 len,
 	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);
-- 
2.3.7

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