From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50550) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Utf9O-0006UF-Dw for qemu-devel@nongnu.org; Mon, 01 Jul 2013 10:32:20 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Utf9N-0002OP-1e for qemu-devel@nongnu.org; Mon, 01 Jul 2013 10:32:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:2971) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Utf9M-0002OH-R7 for qemu-devel@nongnu.org; Mon, 01 Jul 2013 10:32:16 -0400 Message-ID: <51D192EC.5000603@redhat.com> Date: Mon, 01 Jul 2013 16:32:12 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <1372438702-20491-1-git-send-email-pbonzini@redhat.com> <1372438702-20491-3-git-send-email-pbonzini@redhat.com> <51D18EA9.8000400@siemens.com> In-Reply-To: <51D18EA9.8000400@siemens.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: Jan Kiszka Cc: "peter.maydell@linaro.org" , "qemu-devel@nongnu.org" Il 01/07/2013 16:14, Jan Kiszka ha scritto: > 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? Yes, the address space is emptied at destruction time. See memory_region_transaction_begin(); as->root = NULL; memory_region_transaction_commit(); in address_space_destroy. Paolo > 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) >> >