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net: fixing a memory leak in if_deregister_com_alloc()
Drain the callbacks upon if_deregister_com_alloc() such that the if_com_free[type] won't be nullified before if_destroy(). Taking fwip(4) as an example, before this fix, kldunload if_fwip will go through the following: 1. fwip_detach() 2. if_free() -> schedule if_destroy() through NET_EPOCH_CALL 3. fwip_detach() returns 4. firewire_modevent(MOD_UNLOAD) -> if_deregister_com_alloc() 5. kernel complains about: Warning: memory type fw_com leaked memory on destroy (1 allocations, 64 bytes leaked). 6. EPOCH runs if_destroy() -> if_free_internal()i By this time, if_com_free[if_alloctype] is NULL since it's already nullified by if_deregister_com_alloc(); hence, firewire_free() won't have a chance to release the allocated fw_com. Reviewed by: hselasky, glebius MFC after: 2 weeks
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@ -4055,6 +4055,14 @@ if_deregister_com_alloc(u_char type)
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("if_deregister_com_alloc: %d not registered", type));
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KASSERT(if_com_free[type] != NULL,
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("if_deregister_com_alloc: %d free not registered", type));
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/*
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* Ensure all pending EPOCH(9) callbacks have been executed. This
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* fixes issues about late invocation of if_destroy(), which leads
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* to memory leak from if_com_alloc[type] allocated if_l2com.
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*/
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epoch_drain_callbacks(net_epoch_preempt);
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if_com_alloc[type] = NULL;
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if_com_free[type] = NULL;
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}
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