From 9c53564af1e00486218a5d345744273ad242ea33 Mon Sep 17 00:00:00 2001
From: Vincent Rischmann <vincent@rischmann.fr>
Date: Mon, 28 Dec 2020 17:53:52 +0100
Subject: [PATCH] fs: fix segfault in Walker.next

`top` might point to invalid memory after a call to self.stack.append
which causes a segfault.

Prevent this by recomputing `top`.

Fixes #7560
---
 lib/std/fs.zig | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/std/fs.zig b/lib/std/fs.zig
index 6880940c03..026bf21c5c 100644
--- a/lib/std/fs.zig
+++ b/lib/std/fs.zig
@@ -2183,7 +2183,7 @@ pub const Walker = struct {
         while (true) {
             if (self.stack.items.len == 0) return null;
             // `top` becomes invalid after appending to `self.stack`.
-            const top = &self.stack.items[self.stack.items.len - 1];
+            var top = &self.stack.items[self.stack.items.len - 1];
             const dirname_len = top.dirname_len;
             if (try top.dir_it.next()) |base| {
                 self.name_buffer.shrink(dirname_len);
@@ -2200,6 +2200,7 @@ pub const Walker = struct {
                             .dir_it = new_dir.iterate(),
                             .dirname_len = self.name_buffer.items.len,
                         });
+                        top = &self.stack.items[self.stack.items.len - 1];
                     }
                 }
                 return Entry{