Btrfs: return error when we specify wrong start to defrag

We need such a sanity check for wrong start when we defrag a file, otherwise,
even with a wrong start that's larger than file size, we can end up changing
not only inode's force compress flag but also FS's incompat flags.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>

1 files changed, 7 insertions, 4 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index ace88c1df540..a74edc797531 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1154,8 +1154,11 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
         u64 new_align = ~((u64)128 * 1024 - 1);
         struct page **pages = NULL;
 
-        if (extent_thresh == 0)
-                extent_thresh = 256 * 1024;
+        if (isize == 0)
+                return 0;
+
+        if (range->start >= isize)
+                return -EINVAL;
 
         if (range->flags & BTRFS_DEFRAG_RANGE_COMPRESS) {
                 if (range->compress_type > BTRFS_COMPRESS_TYPES)
@@ -1164,8 +1167,8 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
                         compress_type = range->compress_type;
         }
 
-        if (isize == 0)
-                return 0;
+        if (extent_thresh == 0)
+                extent_thresh = 256 * 1024;
 
         /*
          * if we were not given a file, allocate a readahead