Commit 058bc4b5 authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

memory: destroy phys_sections one by one 



phys_sections_clear is invoked after the dispatch tree has been
destroyed.  This leaves a window where phys_sections_nb > 0 but the
subpages are not valid anymore, which is a recipe for use-after-free
bugs.

Move the destruction of subpages in phys_sections_clear.  We will
still destroy the subpages when an address space is cleaned up,
because address_space_destroy will clear as->root and commit the
change before it calls address_space_destroy_dispatch.

Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 2c9b15ca

exec.c

+13 −14
Original line number Diff line number Diff line
@@ -754,17 +754,6 @@ hwaddr memory_region_section_get_iotlb(CPUArchState *env, 
static int subpage_register (subpage_t *mmio, uint32_t start, uint32_t end,

                             uint16_t section);

static subpage_t *subpage_init(AddressSpace *as, hwaddr base);

static void destroy_page_desc(uint16_t section_index)

{

    MemoryRegionSection *section = &phys_sections[section_index];

    MemoryRegion *mr = section->mr;



    if (mr->subpage) {

        subpage_t *subpage = container_of(mr, subpage_t, iomem);

        memory_region_destroy(&subpage->iomem);

        g_free(subpage);

    }

}



static void destroy_l2_mapping(PhysPageEntry *lp, unsigned level)

{
@@ -779,8 +768,6 @@ static void destroy_l2_mapping(PhysPageEntry *lp, unsigned level) 
    for (i = 0; i < L2_SIZE; ++i) {

        if (!p[i].is_leaf) {

            destroy_l2_mapping(&p[i], level - 1);

        } else {

            destroy_page_desc(p[i].ptr);

        }

    }

    lp->is_leaf = 0;
@@ -810,9 +797,21 @@ static uint16_t phys_section_add(MemoryRegionSection *section) 
    return phys_sections_nb++;

}



static void phys_section_destroy(MemoryRegion *mr)

{

    if (mr->subpage) {

        subpage_t *subpage = container_of(mr, subpage_t, iomem);

        memory_region_destroy(&subpage->iomem);

        g_free(subpage);

    }

}



static void phys_sections_clear(void)

{

    phys_sections_nb = 0;

    while (phys_sections_nb > 0) {

        MemoryRegionSection *section = &phys_sections[--phys_sections_nb];

        phys_section_destroy(section->mr);

    }

}



static void register_subpage(AddressSpaceDispatch *d, MemoryRegionSection *section)