Merge bitcoin/bitcoin#22932: Add CBlockIndex lock annotations, guard nStatus/nFile/nDataPos/nUndoPos by cs_main

6ea56827842b9b2bd730edc38f3a7b1f46f6247b Guard CBlockIndex::nStatus/nFile/nDataPos/nUndoPos by cs_main (Jon Atack)
5d59ae0ba88849b1eb0d7350871bc19fcd5ef601 Remove/inline ReadRawBlockFromDisk(block_data, pindex, message_start) (Hennadii Stepanov)
eaeeb88768db529b5241ccd42f1e87579908b4df Require IsBlockPruned() to hold mutex cs_main (Jon Atack)
ca47b005770f71aa229ecc1f7b8146a96ff02151 Require CBlockIndex::IsValid() to hold cs_main (Vasil Dimov)
e9f3aa5f6a7b39e8d5f2069617e5e382798d8d60 Require CBlockIndex::RaiseValidity() to hold cs_main (Vasil Dimov)
8ef457cb83fac796f8b6a56977b1016193fc1185 Require CBlockIndex::IsAssumedValid() to hold cs_main (Vasil Dimov)
572393448b4d32f91b92edc84b4200ab52d62422 Require CBlockIndex::GetUndoPos() to hold mutex cs_main (Jon Atack)
2e557ced2830fc54476e598d52225f1679205e7d Require WriteUndoDataForBlock() to hold mutex cs_main (Jon Atack)
6fd4341c10b319399c58d71c4ddeae4417e337d7 Require CBlockIndex::GetBlockPos() to hold mutex cs_main (Jon Atack)

Pull request description:

  Issues:

  - `CBlockIndex` member functions `GetBlockPos()`, `GetUndoPos()`, `IsAssumedValid()`, `RaiseValidity()`, and `IsValid()` and block storage functions `WriteUndoDataForBlock()` and `IsBlockPruned()` are missing thread safety lock annotations to help ensure that they are called with mutex cs_main to avoid bugs like #22895. Doing this also enables the next step:

  - `CBlockIndex::nStatus` may be racy, i.e. potentially accessed by multiple threads, see #17161. A solution is to guard it by cs_main, along with fellow data members `nFile`, `nDataPos` and `nUndoPos`.

  This pull:

  - adds thread safety lock annotations for the functions listed above
  - guards `CBlockIndex::nStatus`, `nFile`, `nDataPos` and `nUndoPos` by cs_main

  How to review and test:
  - debug build with clang and verify there are no `-Wthread-safety-analysis` warnings
  - review the code to verify each annotation or lock is necessary and sensible, or if any are missing
  - look for whether taking a lock can be replaced by a lock annotation instead
  - for more information about Clang thread safety analysis, see
      - https://clang.llvm.org/docs/ThreadSafetyAnalysis.html
      - https://github.com/bitcoin/bitcoin/blob/master/doc/developer-notes.md#lockingmutex-usage-notes
      - https://github.com/bitcoin/bitcoin/blob/master/doc/developer-notes.md#threads-and-synchronization

  Mitigates/potentially closes #17161.

ACKs for top commit:
  laanwj:
    Code review ACK 6ea56827842b9b2bd730edc38f3a7b1f46f6247b

Tree-SHA512: 3ebf429c8623c51f944a7245a2e48d2aa088dec4c4914b40aa6049e89856c1ee8586f6e2e3b65195190566637a33004468b51a781e61a082248748015167569b

2 files changed, 10 insertions, 15 deletions

diff --git a/src/node/blockstorage.cpp b/src/node/blockstorage.cpp
index cbfdcb6f11..62be9f9aac 100644
--- a/src/node/blockstorage.cpp
+++ b/src/node/blockstorage.cpp
@@ -429,6 +429,7 @@ CBlockIndex* BlockManager::GetLastCheckpoint(const CCheckpointData& data)
 
 bool IsBlockPruned(const CBlockIndex* pblockindex)
 {
+    AssertLockHeld(::cs_main);
     return (fHavePruned && !(pblockindex->nStatus & BLOCK_HAVE_DATA) && pblockindex->nTx > 0);
 }
 
@@ -513,7 +514,8 @@ static bool UndoWriteToDisk(const CBlockUndo& blockundo, FlatFilePos& pos, const
 
 bool UndoReadFromDisk(CBlockUndo& blockundo, const CBlockIndex* pindex)
 {
-    FlatFilePos pos = pindex->GetUndoPos();
+    const FlatFilePos pos{WITH_LOCK(::cs_main, return pindex->GetUndoPos())};
+
     if (pos.IsNull()) {
         return error("%s: no undo data available", __func__);
     }
@@ -712,6 +714,7 @@ static bool WriteBlockToDisk(const CBlock& block, FlatFilePos& pos, const CMessa
 
 bool BlockManager::WriteUndoDataForBlock(const CBlockUndo& blockundo, BlockValidationState& state, CBlockIndex* pindex, const CChainParams& chainparams)
 {
+    AssertLockHeld(::cs_main);
     // Write undo information to disk
     if (pindex->GetUndoPos().IsNull()) {
         FlatFilePos _pos;
@@ -818,17 +821,6 @@ bool ReadRawBlockFromDisk(std::vector<uint8_t>& block, const FlatFilePos& pos, c
     return true;
 }
 
-bool ReadRawBlockFromDisk(std::vector<uint8_t>& block, const CBlockIndex* pindex, const CMessageHeader::MessageStartChars& message_start)
-{
-    FlatFilePos block_pos;
-    {
-        LOCK(cs_main);
-        block_pos = pindex->GetBlockPos();
-    }
-
-    return ReadRawBlockFromDisk(block, block_pos, message_start);
-}
-
 /** Store block on disk. If dbp is non-nullptr, the file is known to already reside on disk */
 FlatFilePos BlockManager::SaveBlockToDisk(const CBlock& block, int nHeight, CChain& active_chain, const CChainParams& chainparams, const FlatFilePos* dbp)
 {
diff --git a/src/node/blockstorage.h b/src/node/blockstorage.h
index 78c9210892..42e46797d2 100644
--- a/src/node/blockstorage.h
+++ b/src/node/blockstorage.h
@@ -7,12 +7,15 @@
 
 #include <fs.h>
 #include <protocol.h> // For CMessageHeader::MessageStartChars
+#include <sync.h>
 #include <txdb.h>
 
 #include <atomic>
 #include <cstdint>
 #include <vector>
 
+extern RecursiveMutex cs_main;
+
 class ArgsManager;
 class BlockValidationState;
 class CBlock;
@@ -146,7 +149,8 @@ public:
     /** Get block file info entry for one block file */
     CBlockFileInfo* GetBlockFileInfo(size_t n);
 
-    bool WriteUndoDataForBlock(const CBlockUndo& blockundo, BlockValidationState& state, CBlockIndex* pindex, const CChainParams& chainparams);
+    bool WriteUndoDataForBlock(const CBlockUndo& blockundo, BlockValidationState& state, CBlockIndex* pindex, const CChainParams& chainparams)
+        EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
 
     FlatFilePos SaveBlockToDisk(const CBlock& block, int nHeight, CChain& active_chain, const CChainParams& chainparams, const FlatFilePos* dbp);
 
@@ -163,7 +167,7 @@ public:
 };
 
 //! Check whether the block associated with this index entry is pruned or not.
-bool IsBlockPruned(const CBlockIndex* pblockindex);
+bool IsBlockPruned(const CBlockIndex* pblockindex) EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
 
 void CleanupBlockRevFiles();
 
@@ -181,7 +185,6 @@ void UnlinkPrunedFiles(const std::set<int>& setFilesToPrune);
 bool ReadBlockFromDisk(CBlock& block, const FlatFilePos& pos, const Consensus::Params& consensusParams);
 bool ReadBlockFromDisk(CBlock& block, const CBlockIndex* pindex, const Consensus::Params& consensusParams);
 bool ReadRawBlockFromDisk(std::vector<uint8_t>& block, const FlatFilePos& pos, const CMessageHeader::MessageStartChars& message_start);
-bool ReadRawBlockFromDisk(std::vector<uint8_t>& block, const CBlockIndex* pindex, const CMessageHeader::MessageStartChars& message_start);
 
 bool UndoReadFromDisk(CBlockUndo& blockundo, const CBlockIndex* pindex);