syzbot

panic: WARNING: circular locking detected: kernel.fsContextMutex -> kernfs.filesystemRWMutex:
	goroutine 437 [running]:
	gvisor.dev/gvisor/pkg/sync/locking.(*ancestorsAtomicPtrMap).RangeRepeatable(0xc0003458e0, 0xc000bf38d8)
		bazel-out/k8-fastbuild/bin/pkg/sync/locking/atomicptrmap_ancestors_unsafe.go:440 +0x314
	gvisor.dev/gvisor/pkg/sync/locking.checkLock(0xc000345050, 0xc0003458c0, {0x0, 0x0, 0x0})
		pkg/sync/locking/lockdep.go:112 +0x4eb
	gvisor.dev/gvisor/pkg/sync/locking.AddGLock(0xc000345050, 0xffffffffffffffff)
		pkg/sync/locking/lockdep.go:144 +0x37b
	gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs.(*filesystemRWMutex).Lock(0xc0009fc4d0)
		bazel-out/k8-fastbuild/bin/pkg/sentry/fsimpl/kernfs/filesystem_mutex.go:31 +0x4d
	gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs.(*Dentry).DecRef(0xc000857c20, {0x21b8bb0, 0xc000ede008})
		pkg/sentry/fsimpl/kernfs/kernfs.go:303 +0x116
	gvisor.dev/gvisor/pkg/sentry/vfs.(*Dentry).DecRef(0xc000857c20, {0x21b8bb0, 0xc000ede008})
		pkg/sentry/vfs/dentry.go:156 +0x68
	gvisor.dev/gvisor/pkg/sentry/vfs.VirtualDentry.DecRef({0xc0001d5130?, 0xc000857c20?}, {0x21b8bb0, 0xc000ede008})
		pkg/sentry/vfs/vfs.go:1114 +0x5b
	gvisor.dev/gvisor/pkg/sentry/kernel.(*FSContext).destroy(0xc000bffcc0, {0x21b8bb0, 0xc000ede008})
		pkg/sentry/kernel/fs_context.go:73 +0x16d
	gvisor.dev/gvisor/pkg/sentry/kernel.(*FSContext).DecRef.func1()
		pkg/sentry/kernel/fs_context.go:87 +0x59
	gvisor.dev/gvisor/pkg/sentry/kernel.(*FSContextRefs).DecRef(0xc000bffcc0, 0xc000bf3d10)
		bazel-out/k8-fastbuild/bin/pkg/sentry/kernel/fs_context_refs.go:133 +0xb4
	gvisor.dev/gvisor/pkg/sentry/kernel.(*FSContext).DecRef(0xc000bffcc0, {0x21b8bb0, 0xc000ede008})
		pkg/sentry/kernel/fs_context.go:86 +0xa5
	gvisor.dev/gvisor/pkg/sentry/kernel.(*runExitMain).execute(0xc000ede008?, 0xc000ede008)
		pkg/sentry/kernel/task_exit.go:301 +0x7d3
	gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).run(0xc000ede008, 0x4b)
		pkg/sentry/kernel/task_run.go:97 +0x402
	created by gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start in goroutine 396
		pkg/sentry/kernel/task_start.go:416 +0x17e
	
	known lock chain: kernfs.filesystemRWMutex -> kernel.taskMutex -> kernel.fsContextMutex
	
	====== kernfs.filesystemRWMutex -> kernel.taskMutex =====
	goroutine 134 [running]:
	gvisor.dev/gvisor/pkg/sentry/kernel.(*taskMutex).Lock(0xc0009789a0)
		bazel-out/k8-fastbuild/bin/pkg/sentry/kernel/task_mutex.go:35 +0x4d
	gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).GetNetworkNamespace(0xc000978008)
		pkg/sentry/kernel/task_net.go:48 +0x4d
	gvisor.dev/gvisor/pkg/sentry/fsimpl/proc.(*filesystem).newTaskNetDir(0xc0001ca480, {0x21b8bb0, 0xc000978008}, 0xc000978008)
		pkg/sentry/fsimpl/proc/task_net.go:47 +0x132
	gvisor.dev/gvisor/pkg/sentry/fsimpl/proc.(*filesystem).newTaskInode(0xc0001ca480, {0x21b8bb0, 0xc000978008}, 0xc000978008, 0xc0001df5e0, 0x1, 0x0)
		pkg/sentry/fsimpl/proc/task.go:77 +0x12d3
	gvisor.dev/gvisor/pkg/sentry/fsimpl/proc.(*tasksInode).Lookup(0xc0006d8008, {0x21b8bb0, 0xc000978008}, {0x1fa0b75, 0x1})
		pkg/sentry/fsimpl/proc/tasks.go:147 +0x3c6
	gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs.(*Filesystem).revalidateChildLocked(0xc0001ca480, {0x21b8bb0, 0xc000978008}, 0xc00031c5e0, 0xc000d033b0, {0x1fa0b75, 0x1})
		pkg/sentry/fsimpl/kernfs/filesystem.go:127 +0x3eb
	gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs.(*Filesystem).stepExistingLocked(0xc0001ca480, {0x21b8bb0, 0xc000978008}, 0xc000300908, 0xc000d033b0)
		pkg/sentry/fsimpl/kernfs/filesystem.go:74 +0x459
	gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs.(*Filesystem).walkExistingLocked(0xc0001ca480, {0x21b8bb0, 0xc000978008}, 0xc000300908)
		pkg/sentry/fsimpl/kernfs/filesystem.go:197 +0x106
	gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs.(*Filesystem).ReadlinkAt(0xc0001ca480, {0x21b8bb0, 0xc000978008}, 0xc000300908)
		pkg/sentry/fsimpl/kernfs/filesystem.go:696 +0x14a
	gvisor.dev/gvisor/pkg/sentry/vfs.(*VirtualFilesystem).ReadlinkAt(0xc00031c5e0, {0x21b8bb0, 0xc000978008}, 0xc000288540, 0xc000049598)
		pkg/sentry/vfs/vfs.go:512 +0x109
	gvisor.dev/gvisor/pkg/sentry/syscalls/linux.readlinkat(0xc000978008, 0xffffff9c, 0xc000128070, 0xc00013ad00, 0x80)
		pkg/sentry/syscalls/linux/sys_file.go:1096 +0x305
	gvisor.dev/gvisor/pkg/sentry/syscalls/linux.Readlinkat(0xc000978008, 0x457b27?, {{0xffffffffffffff9c}, {0xc000128070}, {0xc00013ad00}, {0x80}, {0x0}, {0x0}})
		pkg/sentry/syscalls/linux/sys_file.go:1067 +0xc6
	gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).executeSyscall(0xc000978008, 0x10b, {{0xffffffffffffff9c}, {0xc000128070}, {0xc00013ad00}, {0x80}, {0x0}, {0x0}})
		pkg/sentry/kernel/task_syscall.go:143 +0xb90
	gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallInvoke(0xc000978008, 0x10b, {{0xffffffffffffff9c}, {0xc000128070}, {0xc00013ad00}, {0x80}, {0x0}, {0x0}})
		pkg/sentry/kernel/task_syscall.go:323 +0x85
	gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallEnter(0xc000978008, 0x10b, {{0xffffffffffffff9c}, {0xc000128070}, {0xc00013ad00}, {0x80}, {0x0}, {0x0}})
		pkg/sentry/kernel/task_syscall.go:283 +0xc7
	gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscall(0xc000978008)
		pkg/sentry/kernel/task_syscall.go:258 +0x53e
	gvisor.dev/gvisor/pkg/sentry/kernel.(*runApp).execute(0xc000978008?, 0xc000978008)
		pkg/sentry/kernel/task_run.go:269 +0x220c
	gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).run(0xc000978008, 0x1)
		pkg/sentry/kernel/task_run.go:97 +0x402
	created by gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start in goroutine 1
		pkg/sentry/kernel/task_start.go:416 +0x17e
	
	====== kernel.taskMutex -> kernel.fsContextMutex =====
	goroutine 108 [running]:
	gvisor.dev/gvisor/pkg/sentry/kernel.(*fsContextMutex).Lock(0xc000c92f88)
		bazel-out/k8-fastbuild/bin/pkg/sentry/kernel/fs_context_mutex.go:33 +0x4d
	gvisor.dev/gvisor/pkg/sentry/kernel.(*FSContext).Fork(0xc000c92f80)
		pkg/sentry/kernel/fs_context.go:95 +0x65
	gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Unshare(0xc0005cd208, 0x20000)
		pkg/sentry/kernel/task_clone.go:706 +0x1207
	gvisor.dev/gvisor/pkg/sentry/syscalls/linux.Unshare(0xc0005cd208, 0x457b27?, {{0x20000}, {0x7}, {0x7f2183d3daf0}, {0x0}, {0x0}, {0x564f95bb66c0}})
		pkg/sentry/syscalls/linux/sys_thread.go:453 +0xd5
	gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).executeSyscall(0xc0005cd208, 0x110, {{0x20000}, {0x7}, {0x7f2183d3daf0}, {0x0}, {0x0}, {0x564f95bb66c0}})
		pkg/sentry/kernel/task_syscall.go:143 +0xb90
	gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallInvoke(0xc0005cd208, 0x110, {{0x20000}, {0x7}, {0x7f2183d3daf0}, {0x0}, {0x0}, {0x564f95bb66c0}})
		pkg/sentry/kernel/task_syscall.go:323 +0x85
	gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscallEnter(0xc0005cd208, 0x110, {{0x20000}, {0x7}, {0x7f2183d3daf0}, {0x0}, {0x0}, {0x564f95bb66c0}})
		pkg/sentry/kernel/task_syscall.go:283 +0xc7
	gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).doSyscall(0xc0005cd208)
		pkg/sentry/kernel/task_syscall.go:258 +0x53e
	gvisor.dev/gvisor/pkg/sentry/kernel.(*runApp).execute(0xc0005cd208?, 0xc0005cd208)
		pkg/sentry/kernel/task_run.go:269 +0x220c
	gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).run(0xc0005cd208, 0x18)
		pkg/sentry/kernel/task_run.go:97 +0x402
	created by gvisor.dev/gvisor/pkg/sentry/kernel.(*Task).Start in goroutine 151
		pkg/sentry/kernel/task_start.go:416 +0x17e