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Fixes a race condition in CreateNewBlock and a future null deref on testnet.

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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.
This commit is contained in:
Gregory Maxwell 2012-10-24 01:41:52 -04:00
parent 675a39fc4f
commit faff50d129
1 changed files with 3 additions and 2 deletions
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5
src/main.cpp
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@ -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 // 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 // two in the chain that violate it. This prevents exploiting the issue against nodes in their
// initial block download. // 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"))); (pindex->nHeight==91880 && pindex->GetBlockHash() == uint256("0x00000000000743f190a18c5577a3c2d2a1f610ae9601ac046a38084ccb7cd721")));
if (fEnforceBIP30) { if (fEnforceBIP30) {
for (unsigned int i=0; i<vtx.size(); i++) { for (unsigned int i=0; i<vtx.size(); i++) {
@ -3750,7 +3751,6 @@ CScript scriptDummy(std::vector<unsigned char>(pszDummy, pszDummy + sizeof(pszDu
CBlock* CreateNewBlock(CReserveKey& reservekey) CBlock* CreateNewBlock(CReserveKey& reservekey)
{ {
CBlockIndex* pindexPrev = pindexBest;
// Create new block // Create new block
auto_ptr<CBlock> pblock(new CBlock()); auto_ptr<CBlock> pblock(new CBlock());
@ -3795,6 +3795,7 @@ CBlock* CreateNewBlock(CReserveKey& reservekey)
int64 nFees = 0; int64 nFees = 0;
{ {
LOCK2(cs_main, mempool.cs); LOCK2(cs_main, mempool.cs);
CBlockIndex* pindexPrev = pindexBest;
CCoinsViewCache view(*pcoinsTip, true); CCoinsViewCache view(*pcoinsTip, true);
// Priority order to process transactions // Priority order to process transactions