Emil_Shanaty/Hydra-OS
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fix(installer): resolve nested loop ancestry to a fixed point

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Codex
2026-10-13 05:40:36 +03:00
parent 55648c26e9
commit 5ea9da1162
2 changed files with 111 additions and 10 deletions
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hydra/installer.py
+34 -10
View File
@@ -74,6 +74,7 @@ class Topology:
def __init__(self):
self.nodes = {}
self.edges = {}
self.parents = {}
self.protected = set()
@classmethod
@@ -112,6 +113,7 @@ class Topology:
raise InstallError('Inconsistent duplicate lsblk node')
result.nodes[path] = node
result.edges.setdefault(path, set())
result.parents.setdefault(path, set())
if any(m for m in mounts):
result.protected.add(path)
pkname = node.get('pkname')
@@ -168,6 +170,17 @@ class Topology:
def link(self, child, parent):
if child == parent or child not in self.nodes or parent not in self.nodes:
raise InstallError('Unresolved or cyclic block-device parent')
# Backing links discovered after lsblk must obey the same directed
# ancestry rule. An undirected shared disk is not itself a cycle.
seen, pending = set(), [parent]
while pending:
current = pending.pop()
if current == child:
raise InstallError('Cyclic block-device backing ancestry')
if current not in seen:
seen.add(current)
pending.extend(self.parents[current] - seen)
self.parents[child].add(parent)
self.edges[child].add(parent)
self.edges[parent].add(child)
@@ -240,16 +253,6 @@ class SystemProbe:
source = self._block_source(mount, topo)
if source:
topo.protect(source)
# Mounted loops may hide the physical filesystem that stores their file.
for path, node in topo.nodes.items():
if node['type'] == 'loop' and path in topo.protected:
identity = self._loop_backing_identity(path, node['maj:min'])
sources = [p for p, n in topo.nodes.items() if n['maj:min'] == identity]
if len(sources) != 1:
raise InstallError(f'Unknown physical backing for mounted loop: {path} ({identity})')
source = sources[0]
topo.protect(source)
topo.link(path, source)
if not Path(payload).is_file():
raise InstallError(f'Prepared squashfs payload is not a regular file: {payload}')
source = self._source_for_path(self.resolve(payload), topo)
@@ -257,6 +260,27 @@ class SystemProbe:
# tmpfs/overlay payload location cannot establish live-medium ancestry.
raise InstallError('Cannot identify the payload backing block device; use --payload on the mounted live medium')
topo.protect(source)
# Loops can hide further loops, including ancestors of a mounted
# partition or device mapper. Resolve protected components to a fixed
# point, independent of lsblk ordering and payload discovery order.
inspected = set()
while True:
protected_devices = set()
for path in topo.protected:
protected_devices.update(topo.component(path))
pending = [path for path in topo.nodes if path in protected_devices
and topo.nodes[path]['type'] == 'loop' and path not in inspected]
if not pending:
break
for path in pending:
identity = self._loop_backing_identity(path, topo.nodes[path]['maj:min'])
sources = [p for p, n in topo.nodes.items() if n['maj:min'] == identity]
if len(sources) != 1:
raise InstallError(f'Unknown physical backing for mounted loop: {path} ({identity})')
source = sources[0]
topo.link(path, source)
topo.protect(source)
inspected.add(path)
return topo
@staticmethod
tests/test_installer.py
+77
View File
@@ -486,6 +486,83 @@ class RelocatedLiveLoopTests(unittest.TestCase):
self.assertIn('/dev/loop0', topo.component('/dev/sr0'))
class NestedLoopAncestryTests(unittest.TestCase):
def probe(self, backings=None, *, indirect=False, payload_loop=False, shared=False):
loop0 = disk('/dev/loop0', kind='loop', mounts=['/mnt/also'] if shared else [])
loop0['maj:min'] = '7:0'
loop1 = disk('/dev/loop1', kind='loop', mounts=[] if payload_loop else ['/mnt/valuable'])
loop1['maj:min'] = '7:1'
target, unrelated = disk('/dev/vda'), disk('/dev/vdb')
target['maj:min'], unrelated['maj:min'] = '253:0', '253:1'
media = disk('/dev/sr0', kind='rom', mounts=['/run/initramfs/live'])
media['maj:min'] = '11:0'
nodes = [loop0, loop1, target, unrelated, media]
if indirect:
partition = disk('/dev/loop0p1', kind='part', pkname='/dev/loop0')
partition['maj:min'] = '259:0'
nodes.insert(1, partition)
identities = backings or {'/dev/loop0': '253:0',
'/dev/loop1': '253:0' if shared else '259:0' if indirect else '7:0'}
mount = {'source': '/dev/loop1' if payload_loop else '/dev/sr0',
'target': '/payload' if payload_loop else '/run/initramfs/live',
'fstype': 'ext4' if payload_loop else 'iso9660',
'maj:min': '7:1' if payload_loop else '11:0', 'options': 'ro'}
class ReadOnlyRunner:
def run(self, args):
if args[0] == 'lsblk':
return json.dumps({'blockdevices': nodes})
full_mount = {'source': '/dev/sr0', 'target': '/run/initramfs/live',
'fstype': 'iso9660', 'maj:min': '11:0', 'options': 'ro'}
return json.dumps({'filesystems': [mount] if '--target' in args else [full_mount]})
probe = i.SystemProbe(ReadOnlyRunner())
probe.physical_disk = lambda path: path in {'/dev/vda', '/dev/vdb'}
with patch.object(Path, 'is_file', return_value=True), \
patch.object(i.SystemProbe, '_loop_backing_identity',
side_effect=lambda path, expected: identities[path]):
topo = probe.snapshot(i.DEFAULT_PAYLOAD)
probe.snapshot = lambda payload: topo
return probe, topo
def test_reverse_order_nested_loop_refuses_physical_backing(self):
probe, _ = self.probe()
with self.assertRaisesRegex(i.InstallError, 'backs mounted/root/live storage'):
i.validate_request(i.Request('/dev/vda', 'hydratest'), probe)
def test_reverse_order_nested_loop_allows_unrelated_disk(self):
probe, topo = self.probe()
self.assertIn('/dev/vda', topo.component('/dev/loop1'))
self.assertEqual(i.validate_request(i.Request('/dev/vdb', 'hydratest'), probe), '/dev/vdb')
def test_unknown_nested_backing_refuses_unrelated_installation(self):
with self.assertRaisesRegex(i.InstallError, 'Unknown physical backing'):
self.probe({'/dev/loop1': '7:0', '/dev/loop0': '0:99'})
def test_nested_backing_cycles_fail_closed(self):
for backings in ({'/dev/loop1': '7:0', '/dev/loop0': '7:1'},
{'/dev/loop1': '7:1', '/dev/loop0': '253:0'}):
with self.subTest(backings=backings), self.assertRaisesRegex(i.InstallError, '[Cc]yclic'):
self.probe(backings)
def test_nested_backing_through_loop_partition_refuses_disk(self):
probe, _ = self.probe(indirect=True)
with self.assertRaisesRegex(i.InstallError, 'backs mounted/root/live storage'):
i.validate_request(i.Request('/dev/vda', 'hydratest'), probe)
def test_cycle_through_loop_partition_fails_closed(self):
with self.assertRaisesRegex(i.InstallError, '[Cc]yclic'):
self.probe({'/dev/loop1': '259:0', '/dev/loop0': '7:1'}, indirect=True)
def test_unmounted_payload_loop_ancestors_refuse_disk(self):
probe, _ = self.probe(payload_loop=True)
with self.assertRaisesRegex(i.InstallError, 'backs mounted/root/live storage'):
i.validate_request(i.Request('/dev/vda', 'hydratest'), probe)
def test_two_loops_on_same_backing_are_not_a_directed_cycle(self):
probe, topo = self.probe(shared=True)
self.assertIn('/dev/loop0', topo.component('/dev/loop1'))
self.assertEqual(i.validate_request(i.Request('/dev/vdb', 'hydratest'), probe), '/dev/vdb')
class SnapshotTests(unittest.TestCase):
def test_snapshot_connects_live_loop_to_its_physical_backing(self):
with tempfile.TemporaryDirectory() as tmp: