Fix of use-after-free tunnel_handler_100_continue_ua #12561
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From a recent instrumented core taking traffic in production:
```
(gdb) p write_state.vio
$22 = {
cont = 0x0,
cont_handler_name = 0x9046f2 "&HttpTunnel::main_handler",
nbytes = 9223372036854775807,
ndone = 0,
op = 2,
_disabled = false,
buffer = {
mbuf = 0x0,
entry = 0x0
},
vc_server = 0x7faa48983920,
mutex = {
m_ptr = 0x7fa7bfa24a00
}
}
```
Notice that:
* cont is nullptr
* nbytes is 9223372036854775807 (INT64_MAX)
These are the default value of do_io_write when no values are passed to
it. This doesn't happen in a lot of places, but it does currently in
tunnel_handler_100_continue_ua:
```cpp
c->vc->do_io_write();
```
This changes the call to the following more typical way of canceling a
vc write operation:
```cpp
c->vc->do_io_write(nullptr, 0, nullptr);
```
This way when a PluginVC::process_timeout event is processed, the ntodo
will be 0 and thus the non-existent handler will not be called (see
PluginVC.cc):
```cpp
} else if (write_state.vio.op == VIO::WRITE && !write_state.shutdown && write_state.vio.ntodo() > 0) {
```
shinrich
reviewed
Oct 20, 2025
| // Disable any write operation in case there are timeout events. | ||
| if (c->vc != nullptr) { | ||
| c->vc->do_io_write(); | ||
| c->vc->do_io_write(nullptr, 0, nullptr); |
There was a problem hiding this comment.
You may want to pass in "this" as the first argument. I've had problems before with state machines getting lost because a terminal event is delivered to a VIO with no continuation to deliver the terminal event to.
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From a recent instrumented core taking traffic in production:
Notice that:
These are the default value of do_io_write when no values are passed to it. This doesn't happen in a lot of places, but it does currently in tunnel_handler_100_continue_ua:
c->vc->do_io_write();This changes the call to the following more typical way of canceling a vc write operation:
This way when a PluginVC::process_timeout event is processed, the ntodo will be 0 and thus the non-existent handler will not be called (see PluginVC.cc):