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Merge #18487: rpc: Fix rpcRunLater race in walletpassphrase

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7b8e15728d rpc: Fix rpcRunLater race in walletpassphrase (João Barbosa)

Pull request description:

  Release locks before calling `rpcRunLater`.

  Quick explanation: `rpcRunLater` leads to `event_free` which calls `event_del` which can wait for the event callback to finish if it's already running and that callback will try to lock wallet mutex - which is already locked in http thread.

  Fixes #14995 , fixes #18482. Best reviewed with whitespace changes hidden.

ACKs for top commit:
  MarcoFalke:
    ACK 7b8e15728d, only tested that this avoids the node freezing. Did not look at how libevent works or how the deadlock happens or if this breaks other stuff. 📞
  ryanofsky:
    Code review ACK 7b8e15728d. Just updated comment since last review

Tree-SHA512: 17874a2fa7b0e164fb0d7ee4cb7d59650275b8c03476fb291d60af8b758495457660d3912623fb26259fefe84aeba21c0a9e0c6467982ba511f19344ed5413ab
This commit is contained in:
Wladimir J. van der Laan 2020-04-06 20:29:16 +02:00
commit 75021e80ee
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GPG key ID: 1E4AED62986CD25D
1 changed files with 43 additions and 35 deletions
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78
src/wallet/rpcwallet.cpp
View file

@ -1912,44 +1912,52 @@ static UniValue walletpassphrase(const JSONRPCRequest& request)
}, },
}.Check(request); }.Check(request);
auto locked_chain = pwallet->chain().lock(); int64_t nSleepTime;
LOCK(pwallet->cs_wallet); {
auto locked_chain = pwallet->chain().lock();
LOCK(pwallet->cs_wallet);
if (!pwallet->IsCrypted()) { if (!pwallet->IsCrypted()) {
throw JSONRPCError(RPC_WALLET_WRONG_ENC_STATE, "Error: running with an unencrypted wallet, but walletpassphrase was called."); throw JSONRPCError(RPC_WALLET_WRONG_ENC_STATE, "Error: running with an unencrypted wallet, but walletpassphrase was called.");
}
// Note that the walletpassphrase is stored in request.params[0] which is not mlock()ed
SecureString strWalletPass;
strWalletPass.reserve(100);
// TODO: get rid of this .c_str() by implementing SecureString::operator=(std::string)
// Alternately, find a way to make request.params[0] mlock()'d to begin with.
strWalletPass = request.params[0].get_str().c_str();
// Get the timeout
nSleepTime = request.params[1].get_int64();
// Timeout cannot be negative, otherwise it will relock immediately
if (nSleepTime < 0) {
throw JSONRPCError(RPC_INVALID_PARAMETER, "Timeout cannot be negative.");
}
// Clamp timeout
constexpr int64_t MAX_SLEEP_TIME = 100000000; // larger values trigger a macos/libevent bug?
if (nSleepTime > MAX_SLEEP_TIME) {
nSleepTime = MAX_SLEEP_TIME;
}
if (strWalletPass.empty()) {
throw JSONRPCError(RPC_INVALID_PARAMETER, "passphrase can not be empty");
}
if (!pwallet->Unlock(strWalletPass)) {
throw JSONRPCError(RPC_WALLET_PASSPHRASE_INCORRECT, "Error: The wallet passphrase entered was incorrect.");
}
pwallet->TopUpKeyPool();
pwallet->nRelockTime = GetTime() + nSleepTime;
} }
// Note that the walletpassphrase is stored in request.params[0] which is not mlock()ed // rpcRunLater must be called without cs_wallet held otherwise a deadlock
SecureString strWalletPass; // can occur. The deadlock would happen when RPCRunLater removes the
strWalletPass.reserve(100); // previous timer (and waits for the callback to finish if already running)
// TODO: get rid of this .c_str() by implementing SecureString::operator=(std::string) // and the callback locks cs_wallet.
// Alternately, find a way to make request.params[0] mlock()'d to begin with. AssertLockNotHeld(wallet->cs_wallet);
strWalletPass = request.params[0].get_str().c_str();
// Get the timeout
int64_t nSleepTime = request.params[1].get_int64();
// Timeout cannot be negative, otherwise it will relock immediately
if (nSleepTime < 0) {
throw JSONRPCError(RPC_INVALID_PARAMETER, "Timeout cannot be negative.");
}
// Clamp timeout
constexpr int64_t MAX_SLEEP_TIME = 100000000; // larger values trigger a macos/libevent bug?
if (nSleepTime > MAX_SLEEP_TIME) {
nSleepTime = MAX_SLEEP_TIME;
}
if (strWalletPass.empty()) {
throw JSONRPCError(RPC_INVALID_PARAMETER, "passphrase can not be empty");
}
if (!pwallet->Unlock(strWalletPass)) {
throw JSONRPCError(RPC_WALLET_PASSPHRASE_INCORRECT, "Error: The wallet passphrase entered was incorrect.");
}
pwallet->TopUpKeyPool();
pwallet->nRelockTime = GetTime() + nSleepTime;
// Keep a weak pointer to the wallet so that it is possible to unload the // Keep a weak pointer to the wallet so that it is possible to unload the
// wallet before the following callback is called. If a valid shared pointer // wallet before the following callback is called. If a valid shared pointer
// is acquired in the callback then the wallet is still loaded. // is acquired in the callback then the wallet is still loaded.