syzbot

panic: interface conversion: vfs.DentryImpl is *tmpfs.dentry, not *kernfs.Dentry

goroutine 155 [running]:
panic({0x1167ac0, 0xc000cb2db0})
	GOROOT/src/runtime/panic.go:987 +0x3bb fp=0xc00067d470 sp=0xc00067d3b0 pc=0x436abb
runtime.panicdottypeE(...)
	GOROOT/src/runtime/iface.go:262
runtime.panicdottypeI(0xc00067d4b0?, 0x12b6640, 0x11b1600)
	GOROOT/src/runtime/iface.go:272 +0x7c fp=0xc00067d498 sp=0xc00067d470 pc=0x40b45c
gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs.(*Filesystem).MkdirAt(0xc0007508c0, {0x15350c0, 0xc0009f9500}, 0xc0000c2480, {0x8e00?, 0x5e?})
	pkg/sentry/fsimpl/kernfs/filesystem.go:412 +0x805 fp=0xc00067d6c8 sp=0xc00067d498 pc=0x806b25
gvisor.dev/gvisor/pkg/sentry/fsimpl/proc.(*filesystem).MkdirAt(0xc0000f41e0?, {0x15350c0?, 0xc0009f9500?}, 0xc0000c2480?, {0x0?, 0x0?})
	<autogenerated>:1 +0x2e fp=0xc00067d700 sp=0xc00067d6c8 pc=0xc40c2e
gvisor.dev/gvisor/pkg/sentry/vfs.(*VirtualFilesystem).MkdirAt(0xc0005e8e00?, {0x15350c0, 0xc0009f9500}, 0xc0006ea800?, 0xc000ca1e00?, 0xc00067d7f4)
	pkg/sentry/vfs/vfs.go:367 +0x191 fp=0xc00067d760 sp=0xc00067d700 pc=0x796e91
gvisor.dev/gvisor/pkg/sentry/syscalls/linux.mkdirat(0xc0009f9500, 0x4?, 0xc0009f0100?, 0x1ff)
	pkg/sentry/syscalls/linux/sys_file.go:947 +0x28b fp=0xc00067d8e8 sp=0xc00067d760 pc=0xb3f06b
gvisor.dev/gvisor/pkg/sentry/syscalls/linux.Mkdirat(0xc0009f9500?, 0x0?, {{0xffffff9c}, {0x7f21852db5c0}, {0x1ff}, {0x0}, {0x3}, {0x7f21852db2d7}})
	pkg/sentry/syscalls/linux/sys_file.go:934 +0x50 fp=0xc00067d918 sp=0xc00067d8e8 pc=0xb3edb0
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).executeSyscall(0xc0009f9500, 0x102, {{0xffffff9c}, {0x7f21852db5c0}, {0x1ff}, {0x0}, {0x3}, {0x7f21852db2d7}})
	pkg/sentry/kernel/task_syscall.go:142 +0x80b fp=0xc00067dc58 sp=0xc00067d918 pc=0x9d72cb
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallInvoke(0xc0009f9500, 0x0?, {{0xffffff9c}, {0x7f21852db5c0}, {0x1ff}, {0x0}, {0x3}, {0x7f21852db2d7}})
	pkg/sentry/kernel/task_syscall.go:322 +0x54 fp=0xc00067dcb8 sp=0xc00067dc58 pc=0x9d88b4
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallEnter(0xc0001e6220?, 0xc00067de00?, {{0xffffff9c}, {0x7f21852db5c0}, {0x1ff}, {0x0}, {0x3}, {0x7f21852db2d7}})
	pkg/sentry/kernel/task_syscall.go:282 +0x85 fp=0xc00067dd18 sp=0xc00067dcb8 pc=0x9d84a5
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscall(0xc00019a790?)
	pkg/sentry/kernel/task_syscall.go:257 +0x3ac fp=0xc00067de10 sp=0xc00067dd18 pc=0x9d816c
gvisor.dev/gvisor/pkg/sentry/kernel.(*runApp).execute(0xc000a04200?, 0xc0009f9500)
	pkg/sentry/kernel/task_run.go:269 +0x144a fp=0xc00067df48 sp=0xc00067de10 pc=0x9c9c2a
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).run(0xc0009f9500, 0x1c)
	pkg/sentry/kernel/task_run.go:98 +0x25c fp=0xc00067dfc0 sp=0xc00067df48 pc=0x9c80dc
gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start.func1()
	pkg/sentry/kernel/task_start.go:390 +0x2a fp=0xc00067dfe0 sp=0xc00067dfc0 pc=0x9d574a
runtime.goexit()
	src/runtime/asm_amd64.s:1598 +0x1 fp=0xc00067dfe8 sp=0xc00067dfe0 pc=0x46d4c1
created by gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start
	pkg/sentry/kernel/task_start.go:390 +0x105