From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44866) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Utero-0007A0-Kb for qemu-devel@nongnu.org; Mon, 01 Jul 2013 10:14:10 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Uterm-0003oi-Hf for qemu-devel@nongnu.org; Mon, 01 Jul 2013 10:14:08 -0400 Received: from goliath.siemens.de ([192.35.17.28]:23575) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Uterm-0003nY-8r for qemu-devel@nongnu.org; Mon, 01 Jul 2013 10:14:06 -0400 Message-ID: <51D18EA9.8000400@siemens.com> Date: Mon, 01 Jul 2013 16:14:01 +0200 From: Jan Kiszka MIME-Version: 1.0 References: <1372438702-20491-1-git-send-email-pbonzini@redhat.com> <1372438702-20491-3-git-send-email-pbonzini@redhat.com> In-Reply-To: <1372438702-20491-3-git-send-email-pbonzini@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2 02/11] memory: destroy phys_sections one by one List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: "peter.maydell@linaro.org" , "qemu-devel@nongnu.org" On 2013-06-28 18:58, Paolo Bonzini wrote: > phys_sections_clear is invoked after the dispatch tree has been > destroyed. You mean destroy_all_mappings called by mem_begin vs. phys_sections_clear called by core_begin, right? > 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. What ensures that we still destroy the subpages when an address space is cleaned up (address_space_destroy_dispatch)? The fact that an address space has to be / is de facto empty when destroying it? That question also applies on the next patch. Jan > > Signed-off-by: Paolo Bonzini > --- > exec.c | 27 +++++++++++++-------------- > 1 file changed, 13 insertions(+), 14 deletions(-) > > diff --git a/exec.c b/exec.c > index 1118587..e7eadf5 100644 > --- a/exec.c > +++ b/exec.c > @@ -762,17 +762,6 @@ 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) > { > @@ -787,8 +776,6 @@ 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; > @@ -818,9 +805,21 @@ 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) > -- Siemens AG, Corporate Technology, CT RTC ITP SES-DE Corporate Competence Center Embedded Linux