[release-branch.go1.12] all: merge release-branch.go1.12-security into release-branch.go1.12

Change-Id: Ied19fb5f182670c9dc3bd15327d461b203187cf6

VERSION

-go1.12.10
+go1.12.11
\ No newline at end of file

doc/devel/release.html

@@ -105,6 +105,13 @@ See the <a href="https://github.com/golang/go/issues?q=milestone%3AGo1.12.10">Go
 1.12.10 milestone</a> on our issue tracker for details.
 </p>
 
+<p>
+go1.12.11 (released 2019/10/17) includes security fixes to the
+<code>crypto/dsa</code> package.
+See the <a href="https://github.com/golang/go/issues?q=milestone%3AGo1.12.11">Go
+1.12.11 milestone</a> on our issue tracker for details.
+</p>
+
 <h2 id="go1.11">go1.11 (released 2018/08/24)</h2>
 
 <p>

src/crypto/dsa/dsa.go

@@ -279,6 +279,9 @@ func Verify(pub *PublicKey, hash []byte, r, s *big.Int) bool {
 	}
 
 	w := new(big.Int).ModInverse(s, pub.Q)
+	if w == nil {
+		return false
+	}
 
 	n := pub.Q.BitLen()
 	if n&7 != 0 {