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

goroutine 17 [running]:
github.com/google/syzkaller/prog.(*randGen).filename(0xc00061f140, 0xc000534f00, 0xbf58c0, 0x203000, 0xc00060abf8)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:161 +0x2ac
github.com/google/syzkaller/prog.(*BufferType).generate(0xbf58c0, 0xc00061f140, 0xc000534f00, 0xc00007ca00, 0x3185d17971b0e06, 0xc0007759e8, 0x4f0c53, 0xc00068f230)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:646 +0x4fc
github.com/google/syzkaller/prog.(*randGen).generateArgImpl(0xc00061f140, 0xc000534f00, 0x8fd600, 0xbf58c0, 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(0xc00061f140, 0xc000534f00, 0x8fd600, 0xbf58c0, 0xaaaaaaaaaaaaaaaa, 0x38, 0x7437b2, 0x87a299, 0x3)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:530 +0x52
github.com/google/syzkaller/prog.(*PtrType).generate(0xbd2f80, 0xc00061f140, 0xc000534f00, 0x40b7ff, 0xc0006201e0, 0x30, 0x30, 0x8115a0)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:729 +0x84
github.com/google/syzkaller/prog.(*randGen).generateArgImpl(0xc00061f140, 0xc000534f00, 0x8fda60, 0xbd2f80, 0xc000775b00, 0x0, 0x0, 0x0, 0x0, 0x0)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:581 +0x1b6
github.com/google/syzkaller/prog.(*randGen).generateArg(0xc00061f140, 0xc000534f00, 0x8fda60, 0xbd2f80, 0x3, 0x3, 0x0, 0x203000, 0xc000775ce8)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:530 +0x52
github.com/google/syzkaller/prog.(*randGen).generateArgs(0xc00061f140, 0xc000534f00, 0xbc8d60, 0x3, 0x3, 0x8e80c6307deefe47, 0xc000775db0, 0x72beae, 0x7f3580, 0xc0006dd470, ...)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:518 +0x11d
github.com/google/syzkaller/prog.(*randGen).generateParticularCall(0xc00061f140, 0xc000534f00, 0xbde200, 0x8f, 0xc000534f00, 0xc0008071c8)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:462 +0xd1
github.com/google/syzkaller/prog.(*randGen).generateCall(0xc00061f140, 0xc000534f00, 0xc000534e80, 0xc000534f00, 0xc000775e48, 0x7311e7)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/rand.go:454 +0xa4
github.com/google/syzkaller/prog.(*mutator).insertCall(0xc000775ed0, 0x14)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/mutation.go:118 +0xcb
github.com/google/syzkaller/prog.(*Prog).Mutate(0xc000534e80, 0x8f8660, 0xc00068f230, 0x1e, 0xc00073f940, 0xc000658000, 0x8c9, 0x900)
	/syzkaller/gopath/src/github.com/google/syzkaller/prog/mutation.go:32 +0x299
main.(*Proc).loop(0xc00073f9c0)
	/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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