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

goroutine 17 [running]:
github.com/google/syzkaller/prog.(*randGen).filename(0xc000957520, 0xc000328380, 0xbf6040, 0xc000221880, 0xc000442478)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:161 +0x2ac
github.com/google/syzkaller/prog.(*BufferType).generate(0xbf6040, 0xc000957520, 0xc000328380, 0xc00007aa00, 0x77226fe642b9fdde, 0xc0007ef9e8, 0x4f0c53, 0xc000431530)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:646 +0x4fc
github.com/google/syzkaller/prog.(*randGen).generateArgImpl(0xc000957520, 0xc000328380, 0x8fd600, 0xbf6040, 0x200, 0x0, 0x0, 0x0, 0x0, 0x0)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:581 +0x1b6
github.com/google/syzkaller/prog.(*randGen).generateArg(0xc000957520, 0xc000328380, 0x8fd600, 0xbf6040, 0x223c46000, 0x0, 0x7437b2, 0x87a299, 0x3)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:530 +0x52
github.com/google/syzkaller/prog.(*PtrType).generate(0xbd3ac0, 0xc000957520, 0xc000328380, 0x40b7ff, 0xc00078e980, 0x10, 0x10, 0x8115a0)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:729 +0x84
github.com/google/syzkaller/prog.(*randGen).generateArgImpl(0xc000957520, 0xc000328380, 0x8fda60, 0xbd3ac0, 0xc0007efb00, 0x0, 0x0, 0x0, 0x0, 0x0)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:581 +0x1b6
github.com/google/syzkaller/prog.(*randGen).generateArg(0xc000957520, 0xc000328380, 0x8fda60, 0xbd3ac0, 0x1, 0x1, 0x0, 0x203000, 0xc0007efce8)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:530 +0x52
github.com/google/syzkaller/prog.(*randGen).generateArgs(0xc000957520, 0xc000328380, 0xbc4810, 0x1, 0x1, 0x117c8ff75b21d542, 0xc0007efdb0, 0x72beae, 0x7f3580, 0xc000430930, ...)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:518 +0x11d
github.com/google/syzkaller/prog.(*randGen).generateParticularCall(0xc000957520, 0xc000328380, 0xbde5c0, 0x99, 0xc000328380, 0xc000262c90)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:462 +0xd1
github.com/google/syzkaller/prog.(*randGen).generateCall(0xc000957520, 0xc000328380, 0xc000328300, 0xc000328380, 0xc0007efe48, 0x7311e7)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:454 +0xa4
github.com/google/syzkaller/prog.(*mutator).insertCall(0xc0007efed0, 0x14)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/mutation.go:118 +0xcb
github.com/google/syzkaller/prog.(*Prog).Mutate(0xc000328300, 0x8f8660, 0xc000431530, 0x1e, 0xc000434e00, 0xc00069c000, 0x9a0, 0xc00)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/mutation.go:32 +0x299
main.(*Proc).loop(0xc000434e80)
	/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
login: load: 0.78  cmd: