index: prevent race by calling 'CustomInit' prior setting 'synced' flag #27720
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The 'm_synced' flag enables 'BlockConnected' events to be processed by the index. If we set the flag before calling 'CustomInit', we could be dispatching a block connected event to an uninitialized index child class. e.g. BlockFilterIndex, initializes the next filter position inside 'CustomInit'. So, if `CustomInit` is not called prior receiving the block event, the index will use 'next_filter_position=0' which overwrites the first filter in disk.
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ACK 3126454 |
sidhujag
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…r setting 'synced' flag 3126454 index: prevent race by calling 'CustomInit' prior setting 'synced' flag (furszy) Pull request description: Decoupled from bitcoin#27607. Fixed a potential race condition in master (not possible so far) that could become an actual issue soon. Where the index's `CustomAppend` method could be called (from `BlockConnected`) before its `CustomInit` method, causing the index to try to update itself before it is initialized. This could happen because we set the index `m_synced` flag (which enables `BlockConnected` events) before calling to the child class init function (`CustomInit`). So, for example, the block filter index could process a block before initialize the next filter position field and end up overwriting the first stored filter. This race was introduced in bitcoin@bef4e40 from bitcoin#25494. ACKs for top commit: achow101: ACK 3126454 mzumsande: Code review ACK 3126454 TheCharlatan: Nice, ACK 3126454 Tree-SHA512: 7a53fed1d2035cb4c1f331d6ee9f92d499b6cbb618ea534c6440f5a45ff9b3ac4dcff5fb4b88937f45a0be249e3a9c6dc6c3ac77180f12ae25fc56856ba39735
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Decoupled from #27607.
Fixed a potential race condition in master (not possible so far) that could become an actual issue soon.
Where the index's
CustomAppendmethod could be called (fromBlockConnected) before itsCustomInitmethod, causing the index to try to update itself before it is initialized.This could happen because we set the index
m_syncedflag (which enablesBlockConnectedevents)before calling to the child class init function (
CustomInit). So, for example, the block filter index couldprocess a block before initialize the next filter position field and end up overwriting the first stored filter.
This race was introduced in bef4e40 from #25494.