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

goroutine 16 [running]:
github.com/google/syzkaller/prog.(*randGen).filename(0xc0007ee5c0, 0xc000930b40, 0xbf5460, 0x0, 0xc00003ee00)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:161 +0x2ac
github.com/google/syzkaller/prog.(*BufferType).generate(0xbf5460, 0xc0007ee5c0, 0xc000930b40, 0xc000079500, 0x1c214dd84cf5de3b, 0xc0004c99e8, 0x4f0c53, 0xc0004ba720)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:646 +0x4fc
github.com/google/syzkaller/prog.(*randGen).generateArgImpl(0xc0007ee5c0, 0xc000930b40, 0x8fd600, 0xbf5460, 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(0xc0007ee5c0, 0xc000930b40, 0x8fd600, 0xbf5460, 0xaaaaaaaaaaaaaaaa, 0x38, 0x7437b2, 0x87a299, 0x3)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:530 +0x52
github.com/google/syzkaller/prog.(*PtrType).generate(0xbd2860, 0xc0007ee5c0, 0xc000930b40, 0x40b7ff, 0xc0007f0150, 0x30, 0x30, 0x8115a0)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:729 +0x84
github.com/google/syzkaller/prog.(*randGen).generateArgImpl(0xc0007ee5c0, 0xc000930b40, 0x8fda60, 0xbd2860, 0xc0004c9b00, 0x0, 0x0, 0x0, 0x0, 0x0)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:581 +0x1b6
github.com/google/syzkaller/prog.(*randGen).generateArg(0xc0007ee5c0, 0xc000930b40, 0x8fda60, 0xbd2860, 0x3, 0x3, 0xc000930b80, 0x40, 0xc0004c9ce8)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:530 +0x52
github.com/google/syzkaller/prog.(*randGen).generateArgs(0xc0007ee5c0, 0xc000930b40, 0xbc8b20, 0x3, 0x3, 0xd4fc5bf2d1707d34, 0xc0004c9db0, 0x72beae, 0x7f3580, 0xc000747350, ...)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:518 +0x11d
github.com/google/syzkaller/prog.(*randGen).generateParticularCall(0xc0007ee5c0, 0xc000930b40, 0xbddde0, 0x85, 0xc000930b40, 0xc000799d70)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:462 +0xd1
github.com/google/syzkaller/prog.(*randGen).generateCall(0xc0007ee5c0, 0xc000930b40, 0xc000930900, 0xc000930b40, 0xc0004c9e48, 0x7311e7)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:454 +0xa4
github.com/google/syzkaller/prog.(*mutator).insertCall(0xc0004c9ed0, 0x14)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/mutation.go:118 +0xcb
github.com/google/syzkaller/prog.(*Prog).Mutate(0xc000930900, 0x8f8660, 0xc0004ba720, 0x1e, 0xc0006cfe00, 0xc0006f8000, 0x963, 0xc00)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/mutation.go:32 +0x299
main.(*Proc).loop(0xc0006cfe40)
	/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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