record: avoid crash when calling RecordFlushReplyBuffer recursively
RecordFlushReplyBuffer can call itself recursively through WriteClient->CallCallbacks->_CallCallbacks->RecordFlushAllContexts when the recording client's buffer cannot be completely emptied in one WriteClient. When a such a recursion occurs, it will not be broken out of which results in segmentation fault when the stack is exhausted. This patch adds a counter (a flag, really) that guards against this situation, to break out of the recursion. One alternative to this change would be to change _CallCallbacks to check the corresponding counter before the callback loop, but that might affect existing behavior, which may be relied upon. Reviewed-by: Rami Ylimäki <rami.ylimaki@vincit.fi> Signed-off-by: Erkki Seppälä <erkki.seppala@vincit.fi> Signed-off-by: Keith Packard <keithp@keithp.com>
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@ -77,6 +77,7 @@ typedef struct {
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char bufCategory; /* category of protocol in replyBuffer */
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int numBufBytes; /* number of bytes in replyBuffer */
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char replyBuffer[REPLY_BUF_SIZE]; /* buffered recorded protocol */
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int inFlush; /* are we inside RecordFlushReplyBuffer */
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} RecordContextRec, *RecordContextPtr;
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/* RecordMinorOpRec - to hold minor opcode selections for extension requests
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@ -245,8 +246,9 @@ RecordFlushReplyBuffer(
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int len2
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)
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{
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if (!pContext->pRecordingClient || pContext->pRecordingClient->clientGone)
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if (!pContext->pRecordingClient || pContext->pRecordingClient->clientGone || pContext->inFlush)
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return;
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++pContext->inFlush;
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if (pContext->numBufBytes)
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WriteToClient(pContext->pRecordingClient, pContext->numBufBytes,
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(char *)pContext->replyBuffer);
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@ -255,6 +257,7 @@ RecordFlushReplyBuffer(
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WriteToClient(pContext->pRecordingClient, len1, (char *)data1);
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if (len2)
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WriteToClient(pContext->pRecordingClient, len2, (char *)data2);
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--pContext->inFlush;
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} /* RecordFlushReplyBuffer */
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@ -1938,6 +1941,7 @@ ProcRecordCreateContext(ClientPtr client)
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pContext->numBufBytes = 0;
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pContext->pBufClient = NULL;
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pContext->continuedReply = 0;
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pContext->inFlush = 0;
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err = RecordRegisterClients(pContext, client,
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(xRecordRegisterClientsReq *)stuff);
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