RE: [reSIProcate] Bug in BaseConnection (or TcpBaseTransport?)

["Derek MacDonald" <derek@xxxxxxxxxxxxxxx>]

Good find Byron,

 

Is there a test to reproduce this which shows the problem under, say, valgrind?

 

--Derek

 

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From: resiprocate-devel-bounces@xxxxxxxxxxxxxxxxxxx [mailto:resiprocate-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Byron Campen
Sent: Wednesday, May 03, 2006 11:38 AM
To: resiprocate-devel
Subject: [reSIProcate] Bug in BaseConnection (or TcpBaseTransport?)

 

          Here is the relevant code in TcpBaseTransport...

 

*snip*

 

Connection* currConnection = mConnectionManager.getNextRead(fdset);

if (currConnection)

{

if ( fdset.readyToRead(currConnection->getSocket()) ||

currConnection->hasDataToRead() )

{

DebugLog (<< "TcpBaseTransport::processSomeReads() " << *currConnection);

fdset.clear(currConnection->getSocket());

 

int bytesRead = currConnection->read(mStateMachineFifo);

DebugLog (<< "TcpBaseTransport::processSomeReads() "

<< *currConnection << " read=" << bytesRead);

if (bytesRead < 0)

{

DebugLog (<< "Closing connection bytesRead=" << bytesRead);

delete currConnection;

}

}

 

*snip*

 

The problem here is that Connection::read() can result in deletion of currConnection (see the following)

 

from Connection::read()

*snip*

int

Connection::read(Fifo<TransactionMessage>& fifo)

{

std::pair<char*, size_t> writePair = getWriteBuffer();

size_t bytesToRead = resipMin(writePair.second,

static_cast<size_t>(Connection::ChunkSize));

 

assert(bytesToRead > 0);

int bytesRead = read(writePair.first, bytesToRead);

if (bytesRead <= 0)

{

delete [] writePair.first;

return bytesRead;

}

getConnectionManager().touch(this);

preparseNewBytes(bytesRead, fifo); //.dcm. may delete this

return bytesRead;

}

 

*snip*

 

from ConnectionBase::preparseNewBytes()

*snip*

case ReadingHeaders:

{

unsigned int chunkLength = mBufferPos + bytesRead;

char *unprocessedCharPtr;

MsgHeaderScanner::ScanChunkResult scanChunkResult =

mMsgHeaderScanner.scanChunk(mBuffer,

chunkLength,

&unprocessedCharPtr);

if (scanChunkResult == MsgHeaderScanner::scrError)

{

//.jacob. Not a terribly informative warning.

WarningLog(<< "Discarding preparse!");

delete [] mBuffer;

mBuffer = 0;

delete mMessage;

mMessage = 0;

//.jacob. Shouldn't the state also be set here?

delete this;

return;

}

 

*snip*

 

          Long story short, someone throws garbage at us over a Tcp socket, and we corrupt our heap. So, where should the responsibility for deletion of connections lie? If it belongs in ConnectionBase, we need to document this in the header file, in upper case, preferably about 50 times. (Although it looks like the function return cannot be used to discover whether or not deletion occurred, and it appears that this would be difficult to change, so I would argue we need to stop this behavior.) And, as a general principle, I get very angry when my objects delete themselves on a whim. Imagine the fun if I had a stack-allocated Connection that decided to delete itself?

 

          Also, it is worth noting that a virtual destructor has not been declared for TcpConnection, and an explicitly non-virtual destructor has been declared for TlsConnection. I am not sure whether auto-generated destructors are virtual, so there are potentially two more guns aimed at our foot here.

 

Best regards,

Byron Campen