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

goroutine 17 [running]:
github.com/google/syzkaller/prog.(*randGen).filename(0xc0008d3620, 0xc00086d700, 0xbf7440, 0xc0008115d8, 0x4f0c53)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:161 +0x2ac
github.com/google/syzkaller/prog.(*BufferType).generate(0xbf7440, 0xc0008d3620, 0xc00086d700, 0x8fa9a0, 0xc0008d95c0, 0x0, 0x0, 0x0)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:646 +0x4fc
github.com/google/syzkaller/prog.(*randGen).generateArgImpl(0xc0008d3620, 0xc00086d700, 0x8fd600, 0xbf7440, 0xc000811700, 0x0, 0x0, 0x0, 0x0, 0x0)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:581 +0x1b6
github.com/google/syzkaller/prog.(*randGen).generateArg(0xc0008d3620, 0xc00086d700, 0x8fd600, 0xbf7440, 0x0, 0x0, 0x0, 0x0, 0x0)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:530 +0x52
github.com/google/syzkaller/prog.(*randGen).generateArgs(0xc0008d3620, 0xc00086d700, 0xbc72e0, 0x2, 0x2, 0x2a3424000, 0x0, 0xbca960, 0x742bb6, 0x885e27, ...)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:518 +0x11d
github.com/google/syzkaller/prog.(*StructType).generate(0xbca4e0, 0xc0008d3620, 0xc00086d700, 0x10, 0xc7e300, 0xc0008d9500, 0xc0008119f8, 0x4f0c53)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:713 +0x76
github.com/google/syzkaller/prog.(*randGen).generateArgImpl(0xc0008d3620, 0xc00086d700, 0x8fdba0, 0xbca4e0, 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(0xc0008d3620, 0xc00086d700, 0x8fdba0, 0xbca4e0, 0x0, 0x7432d6, 0x882599, 0xb, 0x0)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:530 +0x52
github.com/google/syzkaller/prog.(*UnionType).generate(0xbca320, 0xc0008d3620, 0xc00086d700, 0xb, 0xc7e300, 0x87ddb8, 0xc000811b68, 0x4f0c53)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:720 +0xa3
github.com/google/syzkaller/prog.(*randGen).generateArgImpl(0xc0008d3620, 0xc00086d700, 0x8fdc40, 0xbca320, 0x89fb00, 0x0, 0x0, 0x0, 0x0, 0x0)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:581 +0x1b6
github.com/google/syzkaller/prog.(*randGen).generateArg(0xc0008d3620, 0xc00086d700, 0x8fdc40, 0xbca320, 0xc7e300, 0x7115ee, 0x8fa9a0, 0xc0008d3dc0, 0x8fdba0)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:530 +0x52
github.com/google/syzkaller/prog.(*UnionType).mutate(0xbca960, 0xc0008d3620, 0xc00086d700, 0x8faae0, 0xc0008d3da0, 0xc00086d4c8, 0xc0008cccc0, 0x0, 0xc0008cc701, 0x21a276f68dc7c6df, ...)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/mutation.go:361 +0x26e
github.com/google/syzkaller/prog.(*Target).mutateArg(0xc0000711e0, 0xc0008d3620, 0xc00086d700, 0x8faae0, 0xc0008d3da0, 0xc00086d4c8, 0xc0008cccc0, 0x0, 0x4f0f01, 0xc000811e0f, ...)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/mutation.go:172 +0xe3
github.com/google/syzkaller/prog.(*mutator).mutateArg(0xc000811ed0, 0xa)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/mutation.go:153 +0x231
github.com/google/syzkaller/prog.(*Prog).Mutate(0xc00086d300, 0x8f8660, 0xc000704120, 0x1e, 0xc000301380, 0xc0006d0000, 0x942, 0xc00)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/mutation.go:34 +0x2db
main.(*Proc).loop(0xc000301400)
	/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