From 4b16b245f48980de5abb6b62252d95e8c7ab8ab3 Mon Sep 17 00:00:00 2001
From: Oskar Eichler <oskar@songstats.com>
Date: Sun, 30 Aug 2026 01:02:44 +0200
Subject: [PATCH] Reject negative native ByteBuffer capacity

---
 ext/nio4r/bytebuffer.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/ext/nio4r/bytebuffer.c b/ext/nio4r/bytebuffer.c
index 99e34f2..942656f 100644
--- a/ext/nio4r/bytebuffer.c
+++ b/ext/nio4r/bytebuffer.c
@@ -130,10 +130,16 @@ static size_t NIO_ByteBuffer_memsize(const void *data)
 
 static VALUE NIO_ByteBuffer_initialize(VALUE self, VALUE capacity)
 {
+    int requested_capacity;
     struct NIO_ByteBuffer *buffer;
     TypedData_Get_Struct(self, struct NIO_ByteBuffer, &NIO_ByteBuffer_type, buffer);
 
-    buffer->capacity = NUM2INT(capacity);
+    requested_capacity = NUM2INT(capacity);
+    if (requested_capacity < 0) {
+        rb_raise(rb_eArgError, "negative capacity given");
+    }
+
+    buffer->capacity = requested_capacity;
     buffer->buffer = xmalloc(buffer->capacity);
 
     NIO_ByteBuffer_clear(self);