Merge #15305: [validation] Crash if disconnecting a block fails

a47df13471e3168e2e02023fb20cdf2414141b36 [qa] Test disconnect block failure -> shutdown (Suhas Daftuar)
4433ed0f730cfd60eeba3694ff3c283ce2c0c8ee [validation] Crash if disconnecting a block fails (Suhas Daftuar)

Pull request description:

  If we're unable to disconnect a block during normal operation, then that is a
  failure of our local system (such as disk failure) or the chain that we are on
  (eg CVE-2018-17144), but cannot be due to failure of the (more work) chain that
  we're trying to validate.

  We should abort rather than stay on a less work chain.

  Fixes #14341.

ACKs for top commit:
  practicalswift:
    utACK a47df13471e3168e2e02023fb20cdf2414141b36
  TheBlueMatt:
    utACK a47df13471e3168e2e02023fb20cdf2414141b36. Didn't bother to review the test in detail, it looked fine. Debated whether invalidateblock should ever crash the node, but *not* crashing in the case of hitting a pruned block (which is the only change here) is clearly better, even if there are other cases I'd argue we should crash in.
  ryanofsky:
    utACK a47df13471e3168e2e02023fb20cdf2414141b36. Only change since last review is new comment.
  promag:
    ACK a47df1347, it takes awhile to quit (RPC connection timeouts) but that's unrelated - hope to fix that soon.
  fanquake:
    ACK a47df13471e3168e2e02023fb20cdf2414141b36

Tree-SHA512: 4dec8cef6e7dbbe513c138fc5821a7ceab855e603ece3c16185b51a3830ab7ebbc844a28827bf64e75326f45325991dcb672f13bd7baede53304f27289c4af8d

1 files changed, 6 insertions, 1 deletions

diff --git a/src/validation.cpp b/src/validation.cpp
index 3246d31513..19f4f098d7 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -2185,7 +2185,7 @@ bool CChainState::DisconnectTip(CValidationState& state, const CChainParams& cha
     std::shared_ptr<CBlock> pblock = std::make_shared<CBlock>();
     CBlock& block = *pblock;
     if (!ReadBlockFromDisk(block, pindexDelete, chainparams.GetConsensus()))
-        return AbortNode(state, "Failed to read block");
+        return error("DisconnectTip(): Failed to read block");
     // Apply the block atomically to the chain state.
     int64_t nStart = GetTimeMicros();
     {
@@ -2442,6 +2442,11 @@ bool CChainState::ActivateBestChainStep(CValidationState& state, const CChainPar
             // This is likely a fatal error, but keep the mempool consistent,
             // just in case. Only remove from the mempool in this case.
             UpdateMempoolForReorg(disconnectpool, false);
+
+            // If we're unable to disconnect a block during normal operation,
+            // then that is a failure of our local system -- we should abort
+            // rather than stay on a less work chain.
+            AbortNode(state, "Failed to disconnect block; see debug.log for details");
             return false;
         }
         fBlocksDisconnected = true;