From d0a822eec524522d81ffc7da2bb1baf906b0318a Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Thu, 1 Jul 2021 06:39:17 +0900
Subject: [PATCH] Fix dtoa buffer overrun

https://hackerone.com/reports/1248108
---
 missing/dtoa.c          |  3 ++-
 test/ruby/test_float.rb | 18 ++++++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/missing/dtoa.c b/missing/dtoa.c
index a940eabd91..b7a8302875 100644
--- a/missing/dtoa.c
+++ b/missing/dtoa.c
@@ -1552,6 +1552,7 @@ break2:
 	    if (!*++s || !(s1 = strchr(hexdigit, *s))) goto ret0;
 	    if (*s == '0') {
 		while (*++s == '0');
+		if (!*s) goto ret;
 		s1 = strchr(hexdigit, *s);
 	    }
 	    if (s1 != NULL) {
@@ -1574,7 +1575,7 @@ break2:
 		for (; *s && (s1 = strchr(hexdigit, *s)); ++s) {
 		    adj += aadj * ((s1 - hexdigit) & 15);
 		    if ((aadj /= 16) == 0.0) {
-			while (strchr(hexdigit, *++s));
+			while (*++s && strchr(hexdigit, *s));
 			break;
 		    }
 		}
diff --git a/test/ruby/test_float.rb b/test/ruby/test_float.rb
index 4be2cfeeda..57a46fce92 100644
--- a/test/ruby/test_float.rb
+++ b/test/ruby/test_float.rb
@@ -171,6 +171,24 @@ class TestFloat < Test::Unit::TestCase
       assert_raise(ArgumentError, n += z + "A") {Float(n)}
       assert_raise(ArgumentError, n += z + ".0") {Float(n)}
     end
+
+    x = nil
+    2000.times do
+      x = Float("0x"+"0"*30)
+      break unless x == 0.0
+    end
+    assert_equal(0.0, x, ->{"%a" % x})
+    x = nil
+    2000.times do
+      begin
+        x = Float("0x1."+"0"*270)
+      rescue ArgumentError => e
+        raise unless /"0x1\.0{270}"/ =~ e.message
+      else
+        break
+      end
+    end
+    assert_nil(x, ->{"%a" % x})
   end
 
   def test_divmod