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Avoid usage of deleted connection #5093

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Avoid usage of deleted connection #5093

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1 change: 1 addition & 0 deletions lib/MySQL_Session.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5206,6 +5206,7 @@ int MySQL_Session::handler() {
NEXT_IMMEDIATE(CONNECTING_SERVER);
return handler_ret;
}
myconn = myds->myconn;
handler_minus1_GenerateErrorMessage(myds, myconn, wrong_pass);
RequestEnd(myds, myerr);
handler_minus1_HandleBackendConnection(myds, myconn);
Comment on lines +5209 to 5212
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medium

Your fix is correct and effectively prevents the use-after-free bug.

However, to make the code more robust and prevent similar issues in the future, we could consider a small refactoring. The functions handler_minus1_GenerateErrorMessage and handler_minus1_HandleBackendConnection are passed a myconn pointer that might be stale.

Instead of passing myconn, these functions could retrieve the connection pointer directly from the MySQL_Data_Stream (myds) argument they already receive. This would ensure they always work with the most up-to-date connection state.

For example, handler_minus1_GenerateErrorMessage could be changed like this:

// from
void MySQL_Session::handler_minus1_GenerateErrorMessage(MySQL_Data_Stream *myds, MySQL_Connection *myconn, bool& wrong_pass) {
    // ...
}

// to
void MySQL_Session::handler_minus1_GenerateErrorMessage(MySQL_Data_Stream *myds, bool& wrong_pass) {
    MySQL_Connection *myconn = myds->myconn;
    // ...
}

A similar change could be applied to handler_minus1_HandleBackendConnection.

This would eliminate the need for the myconn = myds->myconn; line here and make the data flow clearer. What do you think?

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