Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754857AbaJCVpA (ORCPT ); Fri, 3 Oct 2014 17:45:00 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:45274 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755395AbaJCVnW (ORCPT ); Fri, 3 Oct 2014 17:43:22 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Stefan Bader , David Vrabel , Boris Ostrovsky Subject: [PATCH 3.16 214/357] x86/xen: dont copy bogus duplicate entries into kernel page tables Date: Fri, 3 Oct 2014 14:30:00 -0700 Message-Id: <20141003212939.956718198@linuxfoundation.org> X-Mailer: git-send-email 2.1.2 In-Reply-To: <20141003212933.458851516@linuxfoundation.org> References: <20141003212933.458851516@linuxfoundation.org> User-Agent: quilt/0.63-1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16-stable review patch. If anyone has any objections, please let me know. ------------------ From: Stefan Bader commit 0b5a50635fc916cf46e3de0b819a61fc3f17e7ee upstream. When RANDOMIZE_BASE (KASLR) is enabled; or the sum of all loaded modules exceeds 512 MiB, then loading modules fails with a warning (and hence a vmalloc allocation failure) because the PTEs for the newly-allocated vmalloc address space are not zero. WARNING: CPU: 0 PID: 494 at linux/mm/vmalloc.c:128 vmap_page_range_noflush+0x2a1/0x360() This is caused by xen_setup_kernel_pagetables() copying level2_kernel_pgt into level2_fixmap_pgt, overwriting many non-present entries. Without KASLR, the normal kernel image size only covers the first half of level2_kernel_pgt and module space starts after that. L4[511]->level3_kernel_pgt[510]->level2_kernel_pgt[ 0..255]->kernel [256..511]->module [511]->level2_fixmap_pgt[ 0..505]->module This allows 512 MiB of of module vmalloc space to be used before having to use the corrupted level2_fixmap_pgt entries. With KASLR enabled, the kernel image uses the full PUD range of 1G and module space starts in the level2_fixmap_pgt. So basically: L4[511]->level3_kernel_pgt[510]->level2_kernel_pgt[0..511]->kernel [511]->level2_fixmap_pgt[0..505]->module And now no module vmalloc space can be used without using the corrupt level2_fixmap_pgt entries. Fix this by properly converting the level2_fixmap_pgt entries to MFNs, and setting level1_fixmap_pgt as read-only. A number of comments were also using the the wrong L3 offset for level2_kernel_pgt. These have been corrected. Signed-off-by: Stefan Bader Signed-off-by: David Vrabel Reviewed-by: Boris Ostrovsky Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/pgtable_64.h | 1 + arch/x86/xen/mmu.c | 27 ++++++++++++--------------- 2 files changed, 13 insertions(+), 15 deletions(-) --- a/arch/x86/include/asm/pgtable_64.h +++ b/arch/x86/include/asm/pgtable_64.h @@ -19,6 +19,7 @@ extern pud_t level3_ident_pgt[512]; extern pmd_t level2_kernel_pgt[512]; extern pmd_t level2_fixmap_pgt[512]; extern pmd_t level2_ident_pgt[512]; +extern pte_t level1_fixmap_pgt[512]; extern pgd_t init_level4_pgt[]; #define swapper_pg_dir init_level4_pgt --- a/arch/x86/xen/mmu.c +++ b/arch/x86/xen/mmu.c @@ -1866,12 +1866,11 @@ static void __init check_pt_base(unsigne * * We can construct this by grafting the Xen provided pagetable into * head_64.S's preconstructed pagetables. We copy the Xen L2's into - * level2_ident_pgt, level2_kernel_pgt and level2_fixmap_pgt. This - * means that only the kernel has a physical mapping to start with - - * but that's enough to get __va working. We need to fill in the rest - * of the physical mapping once some sort of allocator has been set - * up. - * NOTE: for PVH, the page tables are native. + * level2_ident_pgt, and level2_kernel_pgt. This means that only the + * kernel has a physical mapping to start with - but that's enough to + * get __va working. We need to fill in the rest of the physical + * mapping once some sort of allocator has been set up. NOTE: for + * PVH, the page tables are native. */ void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn) { @@ -1902,8 +1901,11 @@ void __init xen_setup_kernel_pagetable(p /* L3_i[0] -> level2_ident_pgt */ convert_pfn_mfn(level3_ident_pgt); /* L3_k[510] -> level2_kernel_pgt - * L3_i[511] -> level2_fixmap_pgt */ + * L3_k[511] -> level2_fixmap_pgt */ convert_pfn_mfn(level3_kernel_pgt); + + /* L3_k[511][506] -> level1_fixmap_pgt */ + convert_pfn_mfn(level2_fixmap_pgt); } /* We get [511][511] and have Xen's version of level2_kernel_pgt */ l3 = m2v(pgd[pgd_index(__START_KERNEL_map)].pgd); @@ -1913,21 +1915,15 @@ void __init xen_setup_kernel_pagetable(p addr[1] = (unsigned long)l3; addr[2] = (unsigned long)l2; /* Graft it onto L4[272][0]. Note that we creating an aliasing problem: - * Both L4[272][0] and L4[511][511] have entries that point to the same + * Both L4[272][0] and L4[511][510] have entries that point to the same * L2 (PMD) tables. Meaning that if you modify it in __va space * it will be also modified in the __ka space! (But if you just * modify the PMD table to point to other PTE's or none, then you * are OK - which is what cleanup_highmap does) */ copy_page(level2_ident_pgt, l2); - /* Graft it onto L4[511][511] */ + /* Graft it onto L4[511][510] */ copy_page(level2_kernel_pgt, l2); - /* Get [511][510] and graft that in level2_fixmap_pgt */ - l3 = m2v(pgd[pgd_index(__START_KERNEL_map + PMD_SIZE)].pgd); - l2 = m2v(l3[pud_index(__START_KERNEL_map + PMD_SIZE)].pud); - copy_page(level2_fixmap_pgt, l2); - /* Note that we don't do anything with level1_fixmap_pgt which - * we don't need. */ if (!xen_feature(XENFEAT_auto_translated_physmap)) { /* Make pagetable pieces RO */ set_page_prot(init_level4_pgt, PAGE_KERNEL_RO); @@ -1937,6 +1933,7 @@ void __init xen_setup_kernel_pagetable(p set_page_prot(level2_ident_pgt, PAGE_KERNEL_RO); set_page_prot(level2_kernel_pgt, PAGE_KERNEL_RO); set_page_prot(level2_fixmap_pgt, PAGE_KERNEL_RO); + set_page_prot(level1_fixmap_pgt, PAGE_KERNEL_RO); /* Pin down new L4 */ pin_pagetable_pfn(MMUEXT_PIN_L4_TABLE, -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/