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Extend functional test for setBlockIndexCandidates UB

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Fix the from-disk subtest to use a separate node so it builds on a
clean genesis block, rather than the leftover chain from the
in-memory subtest.

Change from a two-way to a three-way block race. The UB in the old
LoadChainTip (mutating nSequenceId, a sort key, while the block is
in setBlockIndexCandidates) corrupts the internal tree structure,
resulting in a failed erase that leaves stale blocks in the set
alongside the tip. With only two competing blocks, this is caught
by libstdc++ but not by libc++. A three-way split triggers the bug
on both implementations.

To trigger CheckBlockIndex (where the crashing assertion is), replace
the restart loop with sending a new block after a single restart.
This commit is contained in:
marcofleon 2026-02-13 14:08:11 +00:00
parent 854a6d5a9a
commit 20ae9b98ea
1 changed files with 31 additions and 18 deletions
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49
test/functional/feature_chain_tiebreaks.py
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@ -15,6 +15,9 @@ class ChainTiebreaksTest(BitcoinTestFramework):
self.num_nodes = 2
self.setup_clean_chain = True
def setup_network(self):
self.setup_nodes()
@staticmethod
def send_headers(node, blocks):
"""Submit headers for blocks to node."""
@ -103,27 +106,29 @@ class ChainTiebreaksTest(BitcoinTestFramework):
node.invalidateblock(blocks[0].hash_hex)
def test_chain_split_from_disk(self):
node = self.nodes[0]
node = self.nodes[1]
peer = node.add_p2p_connection(P2PDataStore())
self.generate(node, 1, sync_fun=self.no_op)
self.log.info('Precomputing blocks')
#
# A1
# /
# G
# \
# A2
# /- A1
# /
# G -- B1 --- A2
# \
# \- A3
#
blocks = []
# Construct two blocks building from genesis.
# Construct three equal-work blocks building from the tip.
start_height = node.getblockcount()
genesis_block = node.getblock(node.getblockhash(start_height))
prev_time = genesis_block["time"]
tip_block = node.getblock(node.getbestblockhash())
prev_time = tip_block["time"]
for i in range(0, 2):
for i in range(0, 3):
blocks.append(create_block(
hashprev=int(genesis_block["hash"], 16),
hashprev=int(tip_block["hash"], 16),
tmpl={"height": start_height + 1,
# Make sure each block has a different hash.
"curtime": prev_time + i + 1,
@ -131,16 +136,24 @@ class ChainTiebreaksTest(BitcoinTestFramework):
))
blocks[-1].solve()
# Send blocks and test the last one is not connected
self.log.info('Send A1 and A2. Make sure that only the former connects')
# Send blocks and test that only the first one connects
self.log.info('Send A1, A2, and A3. Make sure that only the former connects')
peer.send_blocks_and_test([blocks[0]], node, success=True)
peer.send_blocks_and_test([blocks[1]], node, success=False)
peer.send_blocks_and_test([blocks[2]], node, success=False)
self.log.info('Restart the node and check that the best tip before restarting matched the ones afterwards')
# Restart and check enough times for this to eventually fail if the logic is broken
for _ in range(10):
self.restart_node(0)
assert_equal(blocks[0].hash_hex, node.getbestblockhash())
# Restart and send a new block
self.restart_node(1)
assert_equal(blocks[0].hash_hex, node.getbestblockhash())
peer = node.add_p2p_connection(P2PDataStore())
next_block = create_block(
hashprev=blocks[0].hash_int,
tmpl={"height": start_height + 2,
"curtime": prev_time + 10,
}
)
next_block.solve()
peer.send_blocks_and_test([next_block], node, success=True)
def run_test(self):
self.test_chain_split_in_memory()