syscall: allow empty string argument to SetsockoptString

Don't panic with "index out of range" on empty string argument. Fixes #31277 Change-Id: I005f9523caec76337cb2ec87272a6be4736bce18 Reviewed-on: https://go-review.googlesource.com/c/go/+/170937 Run-TryBot: Tobias Klauser <[email protected]> TryBot-Result: Gobot Gobot <[email protected]> Reviewed-by: Brad Fitzpatrick <[email protected]>
golang · Apr 5, 2019 · db0c524 · db0c524
1 parent cea4471
commit db0c524
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Showing 2 changed files with 13 additions and 1 deletion.
diff --git a/src/syscall/syscall_unix.go b/src/syscall/syscall_unix.go
@@ -323,7 +323,11 @@ func SetsockoptLinger(fd, level, opt int, l *Linger) (err error) {
 }
 
 func SetsockoptString(fd, level, opt int, s string) (err error) {
-	return setsockopt(fd, level, opt, unsafe.Pointer(&[]byte(s)[0]), uintptr(len(s)))
+	var p unsafe.Pointer
+	if len(s) > 0 {
+		p = unsafe.Pointer(&[]byte(s)[0])
+	}
+	return setsockopt(fd, level, opt, p, uintptr(len(s)))
 }
 
 func SetsockoptTimeval(fd, level, opt int, tv *Timeval) (err error) {

diff --git a/src/syscall/syscall_unix_test.go b/src/syscall/syscall_unix_test.go
@@ -355,3 +355,11 @@ func TestSeekFailure(t *testing.T) {
 		t.Fatalf("Seek(-1, 0, 0) return error with empty message")
 	}
 }
+
+func TestSetsockoptString(t *testing.T) {
+	// should not panic on empty string, see issue #31277
+	err := syscall.SetsockoptString(-1, 0, 0, "")
+	if err == nil {
+		t.Fatalf("SetsockoptString: did not fail")
+	}
+}