forked from TrueCloudLab/neoneo-go
96449d803a
Blockchain passes his own pure unwrapped DAO to (*Blockchain).ComputeNextBlockValidators which means that native RW NEO cache structure stored inside this DAO can be modified by anyone who uses exported ComputeNextBlockValidators Blockchain API, and technically it's valid, and we should allow this, because it's the only purpose of `validators` caching. However, at the same time some RPC server is allowed to request a subsequent wrapped DAO for some test invocation. It means that descendant wrapped DAO eventually will request RW NEO cache and try to `Copy()` the underlying's DAO cache which is in direct use of ComputeNextBlockValidators. Here's the race: ComputeNextBlockValidators called by Consensus service tries to update cached `validators` value, and descendant wrapped DAO created by the RPC server tries to copy DAO's native cache and read the cached `validators` value. So the problem is that native cache not designated to handle concurrent access between parent DAO layer and derived (wrapped) DAO layer. I've carefully reviewed all the usages of native cache, and turns out that the described situation is the only place where parent DAO is used directly to modify its cache concurrently with some descendant DAO that is trying to access the cache. All other usages of native cache (not only NEO, but also all other native contrcts) strictly rely on the hierarchical DAO structure and don't try to perform these concurrent operations between DAO layers. There's also persist operation, but it keeps cache RW lock taken, so it doesn't have this problem as far. Thus, in this commit we rework NEO's `validators` cache value so that it always contain the relevant list for upper Blockchain's DAO and is updated every PostPersist (if needed). Note: we must be very careful extending our native cache in the future, every usage of native cache must be checked against the described problem. Close #2989. Signed-off-by: Anna Shaleva <shaleva.ann@nspcc.ru> |
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| .. | ||
| helpers/policyhelper | ||
| common_test.go | ||
| cryptolib_test.go | ||
| designate_test.go | ||
| gas_test.go | ||
| ledger_test.go | ||
| management_test.go | ||
| neo_test.go | ||
| notary_test.go | ||
| oracle_test.go | ||
| policy_test.go | ||