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Date: Sun, 22 Aug 2004 18:30:41 -0600 (MDT)
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To: tedu@coverity.com
From: "M. Warner Losh" <imp@bsdimp.com>
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cc: hackers@freebsd.org
Subject: Re: use after free bugs
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In message: <41263E77.5040500@coverity.com>
            Ted Unangst <tedu@coverity.com> writes:
: aha_isa.c: aha_isa_attach:  aha_free free "aha", can't use it 
: afterwards, lots of examples.

aha_free doesn't actually free the aha, it just tears down the dma for
the device.  So the sturct aha_softc * that's passed to it is safe to
use after calls to aha_free.

void
aha_free(struct aha_softc *aha)
{
	switch (aha->init_level) {
	default:
	case 8:
	{
		struct sg_map_node *sg_map;

		while ((sg_map = SLIST_FIRST(&aha->sg_maps))!= NULL) {
			SLIST_REMOVE_HEAD(&aha->sg_maps, links);
			bus_dmamap_unload(aha->sg_dmat, sg_map->sg_dmamap);
			bus_dmamem_free(aha->sg_dmat, sg_map->sg_vaddr,
			    sg_map->sg_dmamap);
			free(sg_map, M_DEVBUF);
		}
		bus_dma_tag_destroy(aha->sg_dmat);
	}
	case 7:
		bus_dmamap_unload(aha->ccb_dmat, aha->ccb_dmamap);
	case 6:
		bus_dmamap_destroy(aha->ccb_dmat, aha->ccb_dmamap);
		bus_dmamem_free(aha->ccb_dmat, aha->aha_ccb_array,
		    aha->ccb_dmamap);
	case 5:
		bus_dma_tag_destroy(aha->ccb_dmat);
	case 4:
		bus_dmamap_unload(aha->mailbox_dmat, aha->mailbox_dmamap);
	case 3:
		bus_dmamem_free(aha->mailbox_dmat, aha->in_boxes,
		    aha->mailbox_dmamap);
		bus_dmamap_destroy(aha->mailbox_dmat, aha->mailbox_dmamap);
	case 2:
		bus_dma_tag_destroy(aha->buffer_dmat);
	case 1:
		bus_dma_tag_destroy(aha->mailbox_dmat);
	case 0:
		break;
	}
}

so all the calls to aha_free then the freeing of resoruces are OK.

Warner