@@ -3947,7 +3947,39 @@ retry:
end_write_bio(&epd, ret);
return ret;
}
- ret = flush_write_bio(&epd);
+ /*
+ * If something went wrong, don't allow any metadata write bio to be
+ * submitted.
+ *
+ * This would prevent use-after-free if we had dirty pages not
+ * cleaned up, which can still happen by fuzzed images.
+ *
+ * - Bad extent tree
+ * Allowing existing tree block to be allocated for other trees.
+ *
+ * - Log tree operations
+ * Exiting tree blocks get allocated to log tree, bumps its
+ * generation, then get cleaned in tree re-balance.
+ * Such tree block will not be written back, since it's clean,
+ * thus no WRITTEN flag set.
+ * And after log writes back, this tree block is not traced by
+ * any dirty extent_io_tree.
+ *
+ * - Offending tree block gets re-dirtied from its original owner
+ * Since it has bumped generation, no WRITTEN flag, it can be
+ * reused without COWing. This tree block will not be traced
+ * by btrfs_transaction::dirty_pages.
+ *
+ * Now such dirty tree block will not be cleaned by any dirty
+ * extent io tree. Thus we don't want to submit such wild eb
+ * if the fs already has error.
+ */
+ if (!test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state)) {
+ ret = flush_write_bio(&epd);
+ } else {
+ ret = -EUCLEAN;
+ end_write_bio(&epd, ret);
+ }
return ret;
}