panic: sandbox escaping file name "../file0"

goroutine 16 [running]:
github.com/google/syzkaller/prog.(*randGen).filename(0xc00030c440, 0xc00078bdc0, 0xbf7b20, 0x1, 0x1)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:161 +0x2ac
github.com/google/syzkaller/prog.(*BufferType).generate(0xbf7b20, 0xc00030c440, 0xc00078bdc0, 0xc00007b500, 0x2ce551d0fd31ab48, 0xc0008339e8, 0x4f0c53, 0xc0002a3080)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:646 +0x4fc
github.com/google/syzkaller/prog.(*randGen).generateArgImpl(0xc00030c440, 0xc00078bdc0, 0x8fd600, 0xbf7b20, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:581 +0x1b6
github.com/google/syzkaller/prog.(*randGen).generateArg(0xc00030c440, 0xc00078bdc0, 0x8fd600, 0xbf7b20, 0x0, 0x0, 0x7437b2, 0x87a299, 0x3)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:530 +0x52
github.com/google/syzkaller/prog.(*PtrType).generate(0xbd8b60, 0xc00030c440, 0xc00078bdc0, 0x8, 0x8, 0xc000520118, 0x0, 0xc000221180)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:729 +0x84
github.com/google/syzkaller/prog.(*randGen).generateArgImpl(0xc00030c440, 0xc00078bdc0, 0x8fda60, 0xbd8b60, 0xc000833b00, 0x0, 0x0, 0x0, 0x0, 0x0)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:581 +0x1b6
github.com/google/syzkaller/prog.(*randGen).generateArg(0xc00030c440, 0xc00078bdc0, 0x8fda60, 0xbd8b60, 0xc000520100, 0x1, 0x1, 0x1, 0x1)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:530 +0x52
github.com/google/syzkaller/prog.(*randGen).generateArgs(0xc00030c440, 0xc00078bdc0, 0xbcf9a0, 0x4, 0x4, 0x754e3664de777109, 0xc000833db0, 0x72beae, 0x7f3580, 0xc0002a24b0, ...)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:518 +0x11d
github.com/google/syzkaller/prog.(*randGen).generateParticularCall(0xc00030c440, 0xc00078bdc0, 0xbe1e00, 0x17, 0xc00078bdc0, 0xc0008c3d70)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:462 +0xd1
github.com/google/syzkaller/prog.(*randGen).generateCall(0xc00030c440, 0xc00078bdc0, 0xc00078bb80, 0xc00078bdc0, 0xc000833e48, 0x7311e7)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:454 +0xa4
github.com/google/syzkaller/prog.(*mutator).insertCall(0xc000833ed0, 0x14)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/mutation.go:118 +0xcb
github.com/google/syzkaller/prog.(*Prog).Mutate(0xc00078bb80, 0x8f8660, 0xc0002a3080, 0x1e, 0xc00062f580, 0xc00073c000, 0x9ec, 0xc00)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/mutation.go:32 +0x299
main.(*Proc).loop(0xc00062f5c0)
	/syzkaller/gopath/src/github.com/google/syzkaller/syz-fuzzer/proc.go:99 +0x446created by main.main
	/syzkaller/gopath/src/github.com/google/syzkaller/syz-fuzzer/fuzzer.go:236 +0xfe2
l