From 618398b7d3c0df13dcb3d87540e400665b2c02dc Mon Sep 17 00:00:00 2001
From: Evan Haas <evan@lagerdata.com>
Date: Wed, 6 Apr 2022 23:48:30 -0700
Subject: [PATCH] std.fs: prevent possible integer overflow in Dir.makePath

The call to `makeDir` for the top-level component of `sub_path`
can return `error.FileNotFound` if the directory represented by
`self` has been deleted.

Fixes #11397
---
 lib/std/fs.zig      |  2 +-
 lib/std/fs/test.zig | 10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/lib/std/fs.zig b/lib/std/fs.zig
index 73efccbbfc..052343599e 100644
--- a/lib/std/fs.zig
+++ b/lib/std/fs.zig
@@ -1308,9 +1308,9 @@ pub const Dir = struct {
                     if (end_index == sub_path.len) return;
                 },
                 error.FileNotFound => {
-                    if (end_index == 0) return err;
                     // march end_index backward until next path component
                     while (true) {
+                        if (end_index == 0) return err;
                         end_index -= 1;
                         if (path.isSep(sub_path[end_index])) break;
                     }
diff --git a/lib/std/fs/test.zig b/lib/std/fs/test.zig
index 2899d0412e..82005152e5 100644
--- a/lib/std/fs/test.zig
+++ b/lib/std/fs/test.zig
@@ -610,6 +610,16 @@ test "makePath, put some files in it, deleteTree" {
     }
 }
 
+test "makePath in a directory that no longer exists" {
+    if (builtin.os.tag == .windows) return error.SkipZigTest; // Windows returns FileBusy if attempting to remove an open dir
+
+    var tmp = tmpDir(.{});
+    defer tmp.cleanup();
+    try tmp.parent_dir.deleteTree(&tmp.sub_path);
+
+    try testing.expectError(error.FileNotFound, tmp.dir.makePath("sub-path"));
+}
+
 test "writev, readv" {
     var tmp = tmpDir(.{});
     defer tmp.cleanup();