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author | Stefan Bader <stefan.bader@canonical.com> | 2014-09-02 14:16:01 +0400 |
---|---|---|
committer | David Vrabel <david.vrabel@citrix.com> | 2014-09-10 18:23:42 +0400 |
commit | 0b5a50635fc916cf46e3de0b819a61fc3f17e7ee (patch) | |
tree | 18c086fa571218617a62fa38210af63e1a0eb9f5 | |
parent | 5903c6bd1a48d90b99e207ec2a6a7673cbbb732d (diff) | |
download | linux-0b5a50635fc916cf46e3de0b819a61fc3f17e7ee.tar.xz |
x86/xen: don't copy bogus duplicate entries into kernel page tables
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 <stefan.bader@canonical.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: stable@vger.kernel.org
-rw-r--r-- | arch/x86/include/asm/pgtable_64.h | 1 | ||||
-rw-r--r-- | arch/x86/xen/mmu.c | 27 |
2 files changed, 13 insertions, 15 deletions
diff --git a/arch/x86/include/asm/pgtable_64.h b/arch/x86/include/asm/pgtable_64.h index 5be9063545d2..3874693c0e53 100644 --- 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 diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c index e8a1201c3293..16fb0099b7f2 100644 --- a/arch/x86/xen/mmu.c +++ b/arch/x86/xen/mmu.c @@ -1866,12 +1866,11 @@ static void __init check_pt_base(unsigned long *pt_base, unsigned long *pt_end, * * 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(pgd_t *pgd, unsigned long max_pfn) /* 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(pgd_t *pgd, unsigned long max_pfn) 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(pgd_t *pgd, unsigned long max_pfn) 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, |