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blockstorage: check nPos in ReadRawBlockFromDisk before seeking back

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ReadRawBlockFromDisk assumes a non-null pos that has an nPos >= 8.
This simple check makes the function safer to call in the future,
so callers don't need to worry about causing UB if the pos is null.
This commit is contained in:
Andrew Toth 2024-03-12 12:46:07 -04:00
parent 12dae637a4
commit da338aada7
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1 changed files with 6 additions and 0 deletions
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6
src/node/blockstorage.cpp
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@ -1088,6 +1088,12 @@ bool BlockManager::ReadBlockFromDisk(CBlock& block, const CBlockIndex& index) co
bool BlockManager::ReadRawBlockFromDisk(std::vector<uint8_t>& block, const FlatFilePos& pos) const
{
FlatFilePos hpos = pos;
// If nPos is less than 8 the pos is null and we don't have the block data
// Return early to prevent undefined behavior of unsigned int underflow
if (hpos.nPos < 8) {
LogError("%s: OpenBlockFile failed for %s\n", __func__, pos.ToString());
return false;
}
hpos.nPos -= 8; // Seek back 8 bytes for meta header
AutoFile filein{OpenBlockFile(hpos, true)};
if (filein.IsNull()) {