Btrfs: fix use-after-free when cloning a trailing file hole

The transaction handle was being used after being freed.

Cc: Chris Mason <clm@fb.com>
Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: Chris Mason <clm@fb.com>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 02dc64b..2a99f49 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3142,7 +3142,6 @@ out:
 static void clone_update_extent_map(struct inode *inode,
                                    const struct btrfs_trans_handle *trans,
                                    const struct btrfs_path *path,
-                                   struct btrfs_file_extent_item *fi,
                                    const u64 hole_offset,
                                    const u64 hole_len)
 {
@@ -3157,7 +3156,11 @@ static void clone_update_extent_map(struct inode *inode,
                return;
        }
 
-       if (fi) {
+       if (path) {
+               struct btrfs_file_extent_item *fi;
+
+               fi = btrfs_item_ptr(path->nodes[0], path->slots[0],
+                                   struct btrfs_file_extent_item);
                btrfs_extent_item_to_extent_map(inode, path, fi, false, em);
                em->generation = -1;
                if (btrfs_file_extent_type(path->nodes[0], fi) ==
@@ -3511,18 +3514,15 @@ process_slot:
                                            btrfs_item_ptr_offset(leaf, slot),
                                            size);
                                inode_add_bytes(inode, datal);
-                               extent = btrfs_item_ptr(leaf, slot,
-                                               struct btrfs_file_extent_item);
                        }
 
                        /* If we have an implicit hole (NO_HOLES feature). */
                        if (drop_start < new_key.offset)
                                clone_update_extent_map(inode, trans,
-                                               path, NULL, drop_start,
+                                               NULL, drop_start,
                                                new_key.offset - drop_start);
 
-                       clone_update_extent_map(inode, trans, path,
-                                               extent, 0, 0);
+                       clone_update_extent_map(inode, trans, path, 0, 0);
 
                        btrfs_mark_buffer_dirty(leaf);
                        btrfs_release_path(path);
@@ -3565,12 +3565,10 @@ process_slot:
                        btrfs_end_transaction(trans, root);
                        goto out;
                }
+               clone_update_extent_map(inode, trans, NULL, last_dest_end,
+                                       destoff + len - last_dest_end);
                ret = clone_finish_inode_update(trans, inode, destoff + len,
                                                destoff, olen);
-               if (ret)
-                       goto out;
-               clone_update_extent_map(inode, trans, path, NULL, last_dest_end,
-                                       destoff + len - last_dest_end);
        }
 
 out: