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authorStefan Bader <stefan.bader@canonical.com>2014-09-02 14:16:01 +0400
committerDavid Vrabel <david.vrabel@citrix.com>2014-09-10 18:23:42 +0400
commit0b5a50635fc916cf46e3de0b819a61fc3f17e7ee (patch)
tree18c086fa571218617a62fa38210af63e1a0eb9f5 /arch/x86/include/asm/pgtable_64.h
parent5903c6bd1a48d90b99e207ec2a6a7673cbbb732d (diff)
downloadlinux-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
Diffstat (limited to 'arch/x86/include/asm/pgtable_64.h')
-rw-r--r--arch/x86/include/asm/pgtable_64.h1
1 files changed, 1 insertions, 0 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