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Merge bitcoin/bitcoin#33475: bugfix: miner: fix addPackageTxs unsigned integer overflow

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b807dfcdc5 miner: fix `addPackageTxs` unsigned integer overflow (ismaelsadeeq)

Pull request description:

  This PR fixes an unsigned integer overflow in the `addPackageTxs` method of the `BlockAssembler`.

  The overflow is a rare edge case that might occur on master when a miner reserves 2000 WU and wants to create an block to be empty.

  i.e, by starting with `-blockmaxweight=2000`, `-blockreservedweight=2000`, or just `blockmaxweight=2000`, and then calling the mining interface `createNewBlock` with `blockReservedWeight` set to `2000`.

  Instead of bailing out after going through transactions equivalent to `MAX_CONSECUTIVE_FAILURES`, the loop never breaks until all mempool transactions are visited.

  See https://github.com/bitcoin/bitcoin/pull/33421#issuecomment-3324859282

  The fix avoids the overflow by using addition instead adding `BLOCK_FULL_ENOUGH_WEIGHT_DELTA` to the block weight and comparing it with `m_options.nBlockMaxWeight`.

  Another alternative that preserves the same structure is to use `static_cast`. See c9530cf35d.

  This fix can be tested by cherry-picking the commits from #33421 without the static cast fix and running:

  ```bash
  echo "AQAAAAAAA
  AAnJycnAAAAAAAAAAAAAAAAAA" | base64 --decode > miner.crash

  FUZZ=block_template_cache ./build_fuzz/bin/fuzz miner.crash
  ```

  ---

  This is part of a larger inconsistency in how size/weight is represented in the codebase. It may be worth defining a dedicated type for size/weight.

ACKs for top commit:
  glozow:
    nice, utACK b807dfcdc5
  furszy:
    Code ACK b807dfcdc5

Tree-SHA512: c1d2f7e500f9b0624a4c22a146921a1644017065e6c94d0c5027486392321f5de26c61751a24765e025e45b34c535adfd6d0e2ac809dea6846b99f37d13043c9
This commit is contained in:
merge-script
2025-09-25 08:18:20 -04:00
parent d41b503ae1 b807dfcdc5
commit 05d984b1a4
1 changed files with 2 additions and 2 deletions
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4
src/node/miner.cpp
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@@ -397,8 +397,8 @@ void BlockAssembler::addPackageTxs(int& nPackagesSelected, int& nDescendantsUpda
++nConsecutiveFailed;
if (nConsecutiveFailed > MAX_CONSECUTIVE_FAILURES && nBlockWeight >
m_options.nBlockMaxWeight - BLOCK_FULL_ENOUGH_WEIGHT_DELTA) {
if (nConsecutiveFailed > MAX_CONSECUTIVE_FAILURES && nBlockWeight +
BLOCK_FULL_ENOUGH_WEIGHT_DELTA > m_options.nBlockMaxWeight) {
// Give up if we're close to full and haven't succeeded in a while
break;
}