prog: allow escaping paths but don't generate them

Filename generated escaping paths in the past.
The reason for the check during validation is to
wipe old program from corpuses. Now that they are
hopefully wiped everywhere, we can relax the check
to restrict only filename to not produce escaping paths,
but allow existing programs with escaping paths.
This is useful in particular if we generate syzkaller
programs from strace output.

1 files changed, 9 insertions, 0 deletions

diff --git a/prog/rand.go b/prog/rand.go
index 23b4afcfa..2e028d230 100644
--- a/prog/rand.go
+++ b/prog/rand.go
@@ -157,6 +157,9 @@ func (r *randGen) filename(s *state, typ *BufferType) string {
 	if len(fn) != 0 && fn[len(fn)-1] == 0 {
 		panic(fmt.Sprintf("zero-terminated filename: %q", fn))
 	}
+	if escapingFilename(fn) {
+		panic(fmt.Sprintf("sandbox escaping file name %q", fn))
+	}
 	if !typ.Varlen() {
 		size := typ.Size()
 		if uint64(len(fn)) < size {
@@ -169,6 +172,12 @@ func (r *randGen) filename(s *state, typ *BufferType) string {
 	return fn
 }
 
+func escapingFilename(file string) bool {
+	file = filepath.Clean(file)
+	return len(file) >= 1 && file[0] == '/' ||
+		len(file) >= 2 && file[0] == '.' && file[1] == '.'
+}
+
 var specialFiles = []string{"", "."}
 
 func (r *randGen) filenameImpl(s *state) string {