From 7580065043761b0c04cf06ac4322c5c790760766 Mon Sep 17 00:00:00 2001
From: dansatch <dansatch98@gmail.com>
Date: Sat, 26 Sep 2026 18:57:43 +0100
Subject: [PATCH 1/2] buffer: fix negative index for large buffers

Fix incorrect negative index results for large buffers.
Add tests for number, Buffer and string searches beyond 2 GiB.

Fixes: https://github.com/nodejs/node/issues/66294

Signed-off-by: dansatch <dansatch98@gmail.com>
---
 src/node_buffer.cc                       | 10 ++++-----
 test/pummel/test-buffer-indexof-large.js | 27 ++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 5 deletions(-)
 create mode 100644 test/pummel/test-buffer-indexof-large.js

diff --git a/src/node_buffer.cc b/src/node_buffer.cc
index 7e966e5f3936..aa42ba032c96 100644
--- a/src/node_buffer.cc
+++ b/src/node_buffer.cc
@@ -1158,7 +1158,7 @@ void IndexOfString(const FunctionCallbackInfo<Value>& args) {
   }
 
   args.GetReturnValue().Set(result >= search_end ? -1
-                                                 : static_cast<int>(result));
+                                                 : static_cast<int64_t>(result));
 }
 
 void IndexOfBuffer(const FunctionCallbackInfo<Value>& args) {
@@ -1246,10 +1246,10 @@ void IndexOfBuffer(const FunctionCallbackInfo<Value>& args) {
   }
 
   args.GetReturnValue().Set(result >= search_end ? -1
-                                                 : static_cast<int>(result));
+                                                 : static_cast<int64_t>(result));
 }
 
-int32_t IndexOfNumberImpl(Local<Value> buffer_obj,
+int64_t IndexOfNumberImpl(Local<Value> buffer_obj,
                           const uint32_t needle,
                           const int64_t offset_i64,
                           const int64_t end_i64,
@@ -1276,7 +1276,7 @@ int32_t IndexOfNumberImpl(Local<Value> buffer_obj,
     ptr = nbytes::stringsearch::MemrchrFill(buffer_data, needle, backward_end);
   }
   const uint8_t* ptr_uint8 = static_cast<const uint8_t*>(ptr);
-  return ptr != nullptr ? static_cast<int32_t>(ptr_uint8 - buffer_data) : -1;
+  return ptr != nullptr ? static_cast<int64_t>(ptr_uint8 - buffer_data) : -1;
 }
 
 void SlowIndexOfNumber(const FunctionCallbackInfo<Value>& args) {
@@ -1297,7 +1297,7 @@ void SlowIndexOfNumber(const FunctionCallbackInfo<Value>& args) {
       IndexOfNumberImpl(buffer_obj, needle, offset_i64, end_i64, is_forward));
 }
 
-int32_t FastIndexOfNumber(Local<Value>,
+int64_t FastIndexOfNumber(Local<Value>,
                           Local<Value> buffer_obj,
                           uint32_t needle,
                           int64_t offset_i64,
diff --git a/test/pummel/test-buffer-indexof-large.js b/test/pummel/test-buffer-indexof-large.js
new file mode 100644
index 000000000000..0f0999705417
--- /dev/null
+++ b/test/pummel/test-buffer-indexof-large.js
@@ -0,0 +1,27 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+
+common.skipIf32Bits();
+
+const match = 2 ** 31 + 100;
+let buffer;
+try {
+  buffer = Buffer.allocUnsafe(match + 1);
+} catch (error) {
+  if (error.code === 'ERR_MEMORY_ALLOCATION_FAILED' ||
+      /Array buffer allocation failed/.test(error.message)) {
+    common.skip('insufficient space for Buffer.allocUnsafe');
+  }
+  throw error;
+}
+
+buffer[match] = 0x0a;
+
+assert.strictEqual(buffer.indexOf(0x0a, -1), match);
+assert.strictEqual(buffer.indexOf(Buffer.from([0x0a]), -1), match);
+assert.strictEqual(buffer.indexOf('\n', -1), match);
+assert.strictEqual(buffer.lastIndexOf(0x0a, -1), match);
+assert.strictEqual(buffer.lastIndexOf(Buffer.from([0x0a]), -1), match);
+assert.strictEqual(buffer.lastIndexOf('\n', -1), match);

From 8861a47a475faaa7c1274685173b33a3c16c0f1b Mon Sep 17 00:00:00 2001
From: dansatch <dansatch98@gmail.com>
Date: Sun, 27 Sep 2026 05:09:19 +0100
Subject: [PATCH 2/2] buffer: fix C++ formatting

Signed-off-by: dansatch <dansatch98@gmail.com>
---
 src/node_buffer.cc | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/node_buffer.cc b/src/node_buffer.cc
index aa42ba032c96..8738abeb9f17 100644
--- a/src/node_buffer.cc
+++ b/src/node_buffer.cc
@@ -1157,8 +1157,8 @@ void IndexOfString(const FunctionCallbackInfo<Value>& args) {
                                   is_forward);
   }
 
-  args.GetReturnValue().Set(result >= search_end ? -1
-                                                 : static_cast<int64_t>(result));
+  args.GetReturnValue().Set(
+      result >= search_end ? -1 : static_cast<int64_t>(result));
 }
 
 void IndexOfBuffer(const FunctionCallbackInfo<Value>& args) {
@@ -1245,8 +1245,8 @@ void IndexOfBuffer(const FunctionCallbackInfo<Value>& args) {
                                   is_forward);
   }
 
-  args.GetReturnValue().Set(result >= search_end ? -1
-                                                 : static_cast<int64_t>(result));
+  args.GetReturnValue().Set(
+      result >= search_end ? -1 : static_cast<int64_t>(result));
 }
 
 int64_t IndexOfNumberImpl(Local<Value> buffer_obj,