From faff50d129b6d4b9e6397ac989218e83a26ae692 Mon Sep 17 00:00:00 2001 From: Gregory Maxwell Date: Wed, 24 Oct 2012 01:41:52 -0400 Subject: [PATCH] Fixes a race condition in CreateNewBlock and a future null deref on testnet. CreateNewBlock was reading pindexBest at the start before taking the lock so it was possible to have the the block content not match the prevheader and this can also trigger a newly added assert in ConnectBlock. I noticed this during a code review after twobitcoins reported that ab91bf39 (BIP30 for all blocks) could cause a null dereference on a modified node that mined during the IBD, or on testnet when it reached heights 91842 and 91880 due to CreateNewBlock calling ConnectBlock with pindex->phashBlock NULL. --- src/main.cpp | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/src/main.cpp b/src/main.cpp index be1e947ad..08188f376 100644 --- a/src/main.cpp +++ b/src/main.cpp @@ -1558,7 +1558,8 @@ bool CBlock::ConnectBlock(CBlockIndex* pindex, CCoinsViewCache &view, bool fJust // Now that the whole chain is irreversibly beyond that time it is applied to all blocks except the // two in the chain that violate it. This prevents exploiting the issue against nodes in their // initial block download. - bool fEnforceBIP30 = !((pindex->nHeight==91842 && pindex->GetBlockHash() == uint256("0x00000000000a4d0a398161ffc163c503763b1f4360639393e0e4c8e300e0caec")) || + bool fEnforceBIP30 = (!pindex->phashBlock) || // Enforce on CreateNewBlock invocations which don't have a hash. + !((pindex->nHeight==91842 && pindex->GetBlockHash() == uint256("0x00000000000a4d0a398161ffc163c503763b1f4360639393e0e4c8e300e0caec")) || (pindex->nHeight==91880 && pindex->GetBlockHash() == uint256("0x00000000000743f190a18c5577a3c2d2a1f610ae9601ac046a38084ccb7cd721"))); if (fEnforceBIP30) { for (unsigned int i=0; i(pszDummy, pszDummy + sizeof(pszDu CBlock* CreateNewBlock(CReserveKey& reservekey) { - CBlockIndex* pindexPrev = pindexBest; // Create new block auto_ptr pblock(new CBlock()); @@ -3795,6 +3795,7 @@ CBlock* CreateNewBlock(CReserveKey& reservekey) int64 nFees = 0; { LOCK2(cs_main, mempool.cs); + CBlockIndex* pindexPrev = pindexBest; CCoinsViewCache view(*pcoinsTip, true); // Priority order to process transactions