Reorder dumpwallet so that cs_main functions go first

DEBUG_LOCKORDER expects cs_wallet, cs_main, and cs_KeyStore to be
acquired in that order. However dumpwallet would take these in the order
cs_wallet, cs_KeyStore, cs_main. So when configured with
`--enable-debug`, it is possible to hit the lock order assertion when
using dumpwallet.

To fix this, cs_wallet and cs_KeyStore are no longer locked at the same
time. Instead cs_wallet will be locked first. Then the functions which
lock cs_main will be run. Lastly cs_KeyStore will be locked afterwards.
This avoids the lock order issue.

Furthermore, since GetKeyBirthTimes (only used by dumpwallet) also uses
a function that locks cs_main, and itself also locks cs_KeyStore, the
same reordering is done here.

Author: achow101

src/wallet/rpcdump.cpp

@@ -740,7 +740,7 @@ RPCHelpMan dumpwallet()
     // the user could have gotten from another RPC command prior to now
     wallet.BlockUntilSyncedToCurrentChain();
 
-    LOCK2(wallet.cs_wallet, spk_man.cs_KeyStore);
+    LOCK(wallet.cs_wallet);
 
     EnsureWalletIsUnlocked(wallet);
 
@@ -762,9 +762,16 @@ RPCHelpMan dumpwallet()
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot open wallet dump file");
 
     std::map<CKeyID, int64_t> mapKeyBirth;
-    const std::map<CKeyID, int64_t>& mapKeyPool = spk_man.GetAllReserveKeys();
     wallet.GetKeyBirthTimes(mapKeyBirth);
 
+    int64_t block_time = 0;
+    CHECK_NONFATAL(wallet.chain().findBlock(wallet.GetLastBlockHash(), FoundBlock().time(block_time)));
+
+    // Note: To avoid a lock order issue, access to cs_main must be locked before cs_KeyStore.
+    // So we do the two things in this function that lock cs_main first: GetKeyBirthTimes, and findBlock.
+    LOCK(spk_man.cs_KeyStore);
+
+    const std::map<CKeyID, int64_t>& mapKeyPool = spk_man.GetAllReserveKeys();
     std::set<CScriptID> scripts = spk_man.GetCScripts();
 
     // sort time/key pairs
@@ -779,8 +786,6 @@ RPCHelpMan dumpwallet()
     file << strprintf("# Wallet dump created by Bitcoin %s\n", CLIENT_BUILD);
     file << strprintf("# * Created on %s\n", FormatISO8601DateTime(GetTime()));
     file << strprintf("# * Best block at time of backup was %i (%s),\n", wallet.GetLastBlockHeight(), wallet.GetLastBlockHash().ToString());
-    int64_t block_time = 0;
-    CHECK_NONFATAL(wallet.chain().findBlock(wallet.GetLastBlockHash(), FoundBlock().time(block_time)));
     file << strprintf("#   mined on %s\n", FormatISO8601DateTime(block_time));
     file << "\n";
 

src/wallet/wallet.cpp

@@ -2298,44 +2298,48 @@ void CWallet::GetKeyBirthTimes(std::map<CKeyID, int64_t>& mapKeyBirth) const {
     AssertLockHeld(cs_wallet);
     mapKeyBirth.clear();
 
-    LegacyScriptPubKeyMan* spk_man = GetLegacyScriptPubKeyMan();
-    assert(spk_man != nullptr);
-    LOCK(spk_man->cs_KeyStore);
-
-    // get birth times for keys with metadata
-    for (const auto& entry : spk_man->mapKeyMetadata) {
-        if (entry.second.nCreateTime) {
-            mapKeyBirth[entry.first] = entry.second.nCreateTime;
-        }
-    }
-
     // map in which we'll infer heights of other keys
     std::map<CKeyID, const CWalletTx::Confirmation*> mapKeyFirstBlock;
     CWalletTx::Confirmation max_confirm;
     max_confirm.block_height = GetLastBlockHeight() > 144 ? GetLastBlockHeight() - 144 : 0; // the tip can be reorganized; use a 144-block safety margin
     CHECK_NONFATAL(chain().findAncestorByHeight(GetLastBlockHash(), max_confirm.block_height, FoundBlock().hash(max_confirm.hashBlock)));
-    for (const CKeyID &keyid : spk_man->GetKeys()) {
-        if (mapKeyBirth.count(keyid) == 0)
-            mapKeyFirstBlock[keyid] = &max_confirm;
-    }
 
-    // if there are no such keys, we're done
-    if (mapKeyFirstBlock.empty())
-        return;
+    {
+        LegacyScriptPubKeyMan* spk_man = GetLegacyScriptPubKeyMan();
+        assert(spk_man != nullptr);
+        LOCK(spk_man->cs_KeyStore);
+
+        // get birth times for keys with metadata
+        for (const auto& entry : spk_man->mapKeyMetadata) {
+            if (entry.second.nCreateTime) {
+                mapKeyBirth[entry.first] = entry.second.nCreateTime;
+            }
+        }
+
+        // Prepare to infer birth heights for keys without metadata
+        for (const CKeyID &keyid : spk_man->GetKeys()) {
+            if (mapKeyBirth.count(keyid) == 0)
+                mapKeyFirstBlock[keyid] = &max_confirm;
+        }
 
-    // find first block that affects those keys, if there are any left
-    for (const auto& entry : mapWallet) {
-        // iterate over all wallet transactions...
-        const CWalletTx &wtx = entry.second;
-        if (wtx.m_confirm.status == CWalletTx::CONFIRMED) {
-            // ... which are already in a block
-            for (const CTxOut &txout : wtx.tx->vout) {
-                // iterate over all their outputs
-                for (const auto &keyid : GetAffectedKeys(txout.scriptPubKey, *spk_man)) {
-                    // ... and all their affected keys
-                    auto rit = mapKeyFirstBlock.find(keyid);
-                    if (rit != mapKeyFirstBlock.end() && wtx.m_confirm.block_height < rit->second->block_height) {
-                        rit->second = &wtx.m_confirm;
+        // if there are no such keys, we're done
+        if (mapKeyFirstBlock.empty())
+            return;
+
+        // find first block that affects those keys, if there are any left
+        for (const auto& entry : mapWallet) {
+            // iterate over all wallet transactions...
+            const CWalletTx &wtx = entry.second;
+            if (wtx.m_confirm.status == CWalletTx::CONFIRMED) {
+                // ... which are already in a block
+                for (const CTxOut &txout : wtx.tx->vout) {
+                    // iterate over all their outputs
+                    for (const auto &keyid : GetAffectedKeys(txout.scriptPubKey, *spk_man)) {
+                        // ... and all their affected keys
+                        auto rit = mapKeyFirstBlock.find(keyid);
+                        if (rit != mapKeyFirstBlock.end() && wtx.m_confirm.block_height < rit->second->block_height) {
+                            rit->second = &wtx.m_confirm;
+                        }
                     }
                 }
             }