https://git.ruby-lang.org/ruby.git/commit/?id=b64876ae55

From b64876ae559b05949c6857fb3d76822c2f7c4df2 Mon Sep 17 00:00:00 2001
From: usa <usa@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Sun, 28 Feb 2021 13:47:29 +0000
Subject: merge revision(s) f364564e66d1db1de8e80d669287386595c8bc46: [Backport
 #16269]

	bignum.c (estimate_initial_sqrt): prevent integer overflow

	`Integer.sqrt(0xffff_ffff_ffff_ffff ** 2)` caused assertion failure
	because of integer overflow.  [ruby-core:95453] [Bug #16269]
	---
	 bignum.c                  | 10 +++++++++-
	 test/ruby/test_integer.rb |  3 +++
	 2 files changed, 12 insertions(+), 1 deletion(-)

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_6@67894 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 bignum.c                  | 10 +++++++++-
 test/ruby/test_integer.rb |  3 +++
 version.h                 |  8 ++++----
 3 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/bignum.c b/bignum.c
index ee3b49f..302774b 100644
--- a/bignum.c
+++ b/bignum.c
@@ -6875,7 +6875,15 @@ estimate_initial_sqrt(VALUE *xp, const size_t xn, const BDIGIT *nds, size_t len) https://github.com/ruby/ruby/blob/trunk/bignum.c#L6875
     rshift /= 2;
     rshift += (2-(len&1))*BITSPERDIG/2;
     if (rshift >= 0) {
-	d <<= rshift;
+        if (nlz((BDIGIT)d) + rshift >= BITSPERDIG) {
+            /* (d << rshift) does cause overflow.
+             * example: Integer.sqrt(0xffff_ffff_ffff_ffff ** 2)
+             */
+            d = ~(BDIGIT_DBL)0;
+        }
+        else {
+            d <<= rshift;
+        }
     }
     BDIGITS_ZERO(xds, xn-2);
     bdigitdbl2bary(&xds[xn-2], 2, d);
diff --git a/test/ruby/test_integer.rb b/test/ruby/test_integer.rb
index 69347b6..0f289d8 100644
--- a/test/ruby/test_integer.rb
+++ b/test/ruby/test_integer.rb
@@ -595,6 +595,9 @@ class TestInteger < Test::Unit::TestCase https://github.com/ruby/ruby/blob/trunk/test/ruby/test_integer.rb#L595
       failures << n  unless root*root <= n && (root+1)*(root+1) > n
     end
     assert_empty(failures, bug13440)
+
+    x = 0xffff_ffff_ffff_ffff
+    assert_equal(x, Integer.sqrt(x ** 2), "[ruby-core:95453]")
   end
 
   def test_fdiv
diff --git a/version.h b/version.h
index 373ee70..408caf4 100644
--- a/version.h
+++ b/version.h
@@ -1,10 +1,10 @@ https://github.com/ruby/ruby/blob/trunk/version.h#L1
 #define RUBY_VERSION "2.6.7"
-#define RUBY_RELEASE_DATE "2021-01-31"
-#define RUBY_PATCHLEVEL 153
+#define RUBY_RELEASE_DATE "2021-02-28"
+#define RUBY_PATCHLEVEL 154
 
 #define RUBY_RELEASE_YEAR 2021
-#define RUBY_RELEASE_MONTH 1
-#define RUBY_RELEASE_DAY 31
+#define RUBY_RELEASE_MONTH 2
+#define RUBY_RELEASE_DAY 28
 
 #include "ruby/version.h"
 
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