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

goroutine 16 [running]:
github.com/google/syzkaller/prog.(*randGen).filename(0xc00057b120, 0xc00075ce40, 0xbf78a0, 0x203000, 0xc000061558)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:161 +0x2ac
github.com/google/syzkaller/prog.(*BufferType).generate(0xbf78a0, 0xc00057b120, 0xc00075ce40, 0xc000079500, 0x726c31e15a5c6cb8, 0xc0004d99e8, 0x4f0c53, 0xc000451a70)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:646 +0x4fc
github.com/google/syzkaller/prog.(*randGen).generateArgImpl(0xc00057b120, 0xc00075ce40, 0x8fd600, 0xbf78a0, 0x100, 0x0, 0x0, 0x0, 0x0, 0x0)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:581 +0x1b6
github.com/google/syzkaller/prog.(*randGen).generateArg(0xc00057b120, 0xc00075ce40, 0x8fd600, 0xbf78a0, 0x20647e000, 0x0, 0x7437b2, 0x87a299, 0x3)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:530 +0x52
github.com/google/syzkaller/prog.(*PtrType).generate(0xbd8260, 0xc00057b120, 0xc00075ce40, 0x40b7ff, 0xc000427830, 0x10, 0x10, 0x8115a0)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:729 +0x84
github.com/google/syzkaller/prog.(*randGen).generateArgImpl(0xc00057b120, 0xc00075ce40, 0x8fda60, 0xbd8260, 0xc0004d9b00, 0x0, 0x0, 0x0, 0x0, 0x0)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:581 +0x1b6
github.com/google/syzkaller/prog.(*randGen).generateArg(0xc00057b120, 0xc00075ce40, 0x8fda60, 0xbd8260, 0x1, 0x1, 0x0, 0x203000, 0xc0004d9ce8)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:530 +0x52
github.com/google/syzkaller/prog.(*randGen).generateArgs(0xc00057b120, 0xc00075ce40, 0xbc48f0, 0x1, 0x1, 0x9c299ed1c7dee6e1, 0xc0004d9db0, 0x72beae, 0x7f3580, 0xc0004501b0, ...)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:518 +0x11d
github.com/google/syzkaller/prog.(*randGen).generateParticularCall(0xc00057b120, 0xc00075ce40, 0xbe1980, 0xb, 0xc00075ce40, 0xc000607d40)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:462 +0xd1
github.com/google/syzkaller/prog.(*randGen).generateCall(0xc00057b120, 0xc00075ce40, 0xc00075cc00, 0xc00075ce40, 0xc0004d9e48, 0x7311e7)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:454 +0xa4
github.com/google/syzkaller/prog.(*mutator).insertCall(0xc0004d9ed0, 0x14)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/mutation.go:118 +0xcb
github.com/google/syzkaller/prog.(*Prog).Mutate(0xc00075cc00, 0x8f8660, 0xc000451a70, 0x1e, 0xc000405f40, 0xc0007fa000, 0x6db, 0x900)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/mutation.go:32 +0x299
main.(*Proc).loop(0xc000256080)
	/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
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