K 10
svn:author
V 6
avatar
K 8
svn:date
V 27
2021-04-10T13:13:54.564094Z
K 7
svn:log
V 1007
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()

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

(cherry picked from commit 092f3f081265c68cd8de0234ba8e46560ccc061e)

Git Hash:   50f1778f6e61dd5855f684bdc43c8f1977e11ff0
Git Author: avatar@FreeBSD.org
END