[release-branch.go1.19] cmd/cover: error out if a requested source file contains a newline

cmd/cover uses '//line' directives to map instrumented source files
back to the original source file and line numbers.
Line directives have no way to escape newline characters, so cmd/cover
must not be used with source file paths that contain such characters.

Updates #60515.
Updates #60167.

Change-Id: I6dc039392d59fc3a5a6121ef6ca97b0ab0da5288
Reviewed-on: https://go-review.googlesource.com/c/go/+/501577
Auto-Submit: Bryan Mills <bcmills@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
(cherry picked from commit 3d78c735fc7d213e23383b9744297bd5251dc0e3)
Reviewed-on: https://go-review.googlesource.com/c/go/+/501822

2 files changed, 35 insertions, 0 deletions

diff --git a/src/cmd/cover/cover.go b/src/cmd/cover/cover.go
index 86ef128f2c..d8c4f85708 100644
--- a/src/cmd/cover/cover.go
+++ b/src/cmd/cover/cover.go
@@ -15,6 +15,7 @@ import (
 	"log"
 	"os"
 	"sort"
+	"strings"
 
 	"cmd/internal/edit"
 	"cmd/internal/objabi"
@@ -341,6 +342,9 @@ func annotate(name string) {
 		}
 	}
 
+	if strings.ContainsAny(name, "\r\n") {
+		log.Fatalf("cover: input path contains newline character: %q", name)
+	}
 	fmt.Fprintf(fd, "//line %s:1\n", name)
 	fd.Write(newContent)
 
diff --git a/src/cmd/cover/cover_test.go b/src/cmd/cover/cover_test.go
index 28be231121..8a68911bd3 100644
--- a/src/cmd/cover/cover_test.go
+++ b/src/cmd/cover/cover_test.go
@@ -570,3 +570,34 @@ func run(c *exec.Cmd, t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+func TestSrcPathWithNewline(t *testing.T) {
+	t.Parallel()
+	buildCover(t)
+
+	// srcPath is intentionally not clean so that the path passed to testcover
+	// will not normalize the trailing / to a \ on Windows.
+	srcPath := t.TempDir() + string(filepath.Separator) + "\npackage main\nfunc main() { panic(string([]rune{'u', 'h', '-', 'o', 'h'}))\n/*/main.go"
+	mainSrc := ` package main
+
+func main() {
+	/* nothing here */
+	println("ok")
+}
+`
+	if err := os.MkdirAll(filepath.Dir(srcPath), 0777); err != nil {
+		t.Skipf("creating directory with bogus path: %v", err)
+	}
+	if err := os.WriteFile(srcPath, []byte(mainSrc), 0666); err != nil {
+		t.Skipf("writing file with bogus directory: %v", err)
+	}
+
+	cmd := exec.Command(testcover, "-mode=atomic", srcPath)
+	cmd.Stderr = new(bytes.Buffer)
+	out, err := cmd.Output()
+	t.Logf("%v:\n%s", cmd, out)
+	t.Logf("stderr:\n%s", cmd.Stderr)
+	if err == nil {
+		t.Errorf("unexpected success; want failure due to newline in file path")
+	}
+}