From a93c66e7947591db60a84bb02c1ddb0238dda4db Mon Sep 17 00:00:00 2001
From: Lukas Wirth <lukas@zed.dev>
Date: Mon, 16 Mar 2026 08:43:56 +0100
Subject: [PATCH] markdown_preview: Prevent stackoverflows in markdown parsing
 (#51637)

Fixes ZED-5TR

Release Notes:

- Fixed a stack overflow when parsing deeply nested html in markdown
files
---
 Cargo.lock                                     | 1 +
 crates/markdown_preview/Cargo.toml             | 1 +
 crates/markdown_preview/src/markdown_parser.rs | 3 +++
 3 files changed, 5 insertions(+)

diff --git a/Cargo.lock b/Cargo.lock
index 8d86e9fa9b82978a4309ff4a77dd8388b4626d0b..83606c7414b7ca323001d79a3aed690f2a57f554 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -10247,6 +10247,7 @@ dependencies = [
  "pretty_assertions",
  "pulldown-cmark 0.13.0",
  "settings",
+ "stacksafe",
  "theme",
  "ui",
  "urlencoding",
diff --git a/crates/markdown_preview/Cargo.toml b/crates/markdown_preview/Cargo.toml
index 4baa308f1088341aada1eb2917c2133b8df8c143..c72de7274a407c168e7a3cdd7a253070cc6f858a 100644
--- a/crates/markdown_preview/Cargo.toml
+++ b/crates/markdown_preview/Cargo.toml
@@ -30,6 +30,7 @@ markup5ever_rcdom.workspace = true
 pretty_assertions.workspace = true
 pulldown-cmark.workspace = true
 settings.workspace = true
+stacksafe.workspace = true
 theme.workspace = true
 ui.workspace = true
 urlencoding.workspace = true
diff --git a/crates/markdown_preview/src/markdown_parser.rs b/crates/markdown_preview/src/markdown_parser.rs
index ffd697d0e1bafc2feeccf3a3a7836a224d983860..29ea273f49578bd6ad408a8d57b891f572705c07 100644
--- a/crates/markdown_preview/src/markdown_parser.rs
+++ b/crates/markdown_preview/src/markdown_parser.rs
@@ -10,6 +10,7 @@ use language::LanguageRegistry;
 use markdown::parser::PARSE_OPTIONS;
 use markup5ever_rcdom::RcDom;
 use pulldown_cmark::{Alignment, Event, Parser, Tag, TagEnd};
+use stacksafe::stacksafe;
 use std::{
     cell::RefCell, collections::HashMap, mem, ops::Range, path::PathBuf, rc::Rc, sync::Arc, vec,
 };
@@ -907,6 +908,7 @@ impl<'a> MarkdownParser<'a> {
         elements
     }
 
+    #[stacksafe]
     fn parse_html_node(
         &self,
         source_range: Range<usize>,
@@ -1013,6 +1015,7 @@ impl<'a> MarkdownParser<'a> {
         }
     }
 
+    #[stacksafe]
     fn parse_paragraph(
         &self,
         source_range: Range<usize>,