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>

1 files changed, 9 insertions, 11 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 02dc64bbf1cb..2a99f4987bb1 100644
--- 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: