x86/pti: Filter at vma->vm_page_prot population

commit ce9962bf7e22bb3891655c349faff618922d4a73

0day reported warnings at boot on 32-bit systems without NX support:

attempted to set unsupported pgprot: 8000000000000025 bits: 8000000000000000 supported: 7fffffffffffffff
WARNING: CPU: 0 PID: 1 at
arch/x86/include/asm/pgtable.h:540 handle_mm_fault+0xfc1/0xfe0:
 check_pgprot at arch/x86/include/asm/pgtable.h:535
 (inlined by) pfn_pte at arch/x86/include/asm/pgtable.h:549
 (inlined by) do_anonymous_page at mm/memory.c:3169
 (inlined by) handle_pte_fault at mm/memory.c:3961
 (inlined by) __handle_mm_fault at mm/memory.c:4087
 (inlined by) handle_mm_fault at mm/memory.c:4124

The problem is that due to the recent commit which removed auto-massaging
of page protections, filtering page permissions at PTE creation time is not
longer done, so vma->vm_page_prot is passed unfiltered to PTE creation.

Filter the page protections before they are installed in vma->vm_page_prot.

Fixes: fb43d6cb91 ("x86/mm: Do not auto-massage page protections")
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Kees Cook <keescook@google.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: linux-mm@kvack.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Nadav Amit <namit@vmware.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Link: https://lkml.kernel.org/r/20180420222028.99D72858@viggo.jf.intel.com
CVE-2018-3620
CVE-2018-3646

(cherry picked from commit 316d097c4cd4e7f2ef50c40cff2db266593c4ec4)
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 7818c7fffe04edb660f2f2498ffa6338d05a7e64..2d89cd14193d8c98bf28b7f4597b0913057f25f9 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -51,6 +51,7 @@ config X86
        select ARCH_HAS_DEVMEM_IS_ALLOWED
        select ARCH_HAS_ELF_RANDOMIZE
        select ARCH_HAS_FAST_MULTIPLIER
+       select ARCH_HAS_FILTER_PGPROT
        select ARCH_HAS_FORTIFY_SOURCE
        select ARCH_HAS_GCOV_PROFILE_ALL
        select ARCH_HAS_KCOV                    if X86_64
@@ -268,6 +269,9 @@ config ARCH_HAS_CPU_RELAX
 config ARCH_HAS_CACHE_LINE_SIZE
        def_bool y
 
+config ARCH_HAS_FILTER_PGPROT
+       def_bool y
+
 config HAVE_SETUP_PER_CPU_AREA
        def_bool y
 

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 6125154f2146931f92c3cfe0ca57490f60379819..dc89931a699da17ca3103c2e857e90a297c4b7d0 100644 (file)
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -601,6 +601,11 @@ static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
 
 #define canon_pgprot(p) __pgprot(massage_pgprot(p))
 
+static inline pgprot_t arch_filter_pgprot(pgprot_t prot)
+{
+       return canon_pgprot(prot);
+}
+
 static inline int is_new_memtype_allowed(u64 paddr, unsigned long size,
                                         enum page_cache_mode pcm,
                                         enum page_cache_mode new_pcm)

diff --git a/mm/mmap.c b/mm/mmap.c
index d77f01f5380b574548a5dbcd2a85b5ad9960e50e..065446860cd85bab4af7b1f2e5fa65ed05de8694 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -100,11 +100,20 @@ pgprot_t protection_map[16] __ro_after_init = {
        __S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
 };
 
+#ifndef CONFIG_ARCH_HAS_FILTER_PGPROT
+static inline pgprot_t arch_filter_pgprot(pgprot_t prot)
+{
+       return prot;
+}
+#endif
+
 pgprot_t vm_get_page_prot(unsigned long vm_flags)
 {
-       return __pgprot(pgprot_val(protection_map[vm_flags &
+       pgprot_t ret = __pgprot(pgprot_val(protection_map[vm_flags &
                                (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
                        pgprot_val(arch_vm_get_page_prot(vm_flags)));
+
+       return arch_filter_pgprot(ret);
 }
 EXPORT_SYMBOL(vm_get_page_prot);