From 058bc4b57f9d6b39d9a6748b4049e1be3fde3dac Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Tue, 25 Jun 2013 09:30:48 +0200 Subject: [PATCH] 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: Paolo Bonzini --- exec.c | 27 +++++++++++++-------------- 1 file changed, 13 insertions(+), 14 deletions(-) diff --git a/exec.c b/exec.c index 5094746633..78be4f52a2 100644 --- a/exec.c +++ b/exec.c @@ -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)