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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
committed by Luke Dashjr
parent 3e72516398
commit 2857d51fea
1 changed files with 3 additions and 2 deletions
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5
src/main.cpp
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@@ -1416,7 +1416,8 @@ bool CBlock::ConnectBlock(CTxDB& txdb, CBlockIndex* pindex, bool fJustCheck)
// 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")));
// BIP16 didn't become active until Apr 1 2012
@@ -3460,7 +3461,6 @@ public:
CBlock* CreateNewBlock(CReserveKey& reservekey)
{
CBlockIndex* pindexPrev = pindexBest;
// Create new block
auto_ptr<CBlock> pblock(new CBlock());
@@ -3505,6 +3505,7 @@ CBlock* CreateNewBlock(CReserveKey& reservekey)
int64 nFees = 0;
{
LOCK2(cs_main, mempool.cs);
CBlockIndex* pindexPrev = pindexBest;
CTxDB txdb("r");
// Priority order to process transactions