in_forward: fix connection release on pause memory corruption [Backport to 4.0] #11182
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This change fixes a use after free issue related to connection disposal which caused the event handler to access invalid memory when the memory limits were exceeded during ingestion. In order to overcome this issue we track the plugin instances state and delay the connection cleanup process. Signed-off-by: Leonardo Albertovich <leonardo@alminana.com.ar>
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| ctx->state = state_backup; | ||
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| if (ctx->state == FW_INSTANCE_STATE_PAUSED) { | ||
| fw_conn_del_all(ctx); |
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The collector backs up the plugin state, switches it to FW_INSTANCE_STATE_ACCEPTING_CLIENT, and at the end unconditionally restores the backup before checking for a pause. If in_fw_pause() fires while a connection is being accepted it sets ctx->state to FW_INSTANCE_STATE_PAUSED so it can close connections later, but these lines overwrite that pause state back to the old value and the subsequent fw_conn_del_all(ctx) guard never runs. As a result existing connections remain active and continue ingesting while the input is paused, defeating backpressure. The state should only be restored when it is still ACCEPTING_CLIENT; if the state has become PAUSED we should keep that state and trigger cleanup similar to fw_conn_event.
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Backporting of #11114.
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