x86/mm: Do not auto-massage page protections

A PTE is constructed from a physical address and a pgprotval_t.
__PAGE_KERNEL, for instance, is a pgprot_t and must be converted
into a pgprotval_t before it can be used to create a PTE.  This is
done implicitly within functions like pfn_pte() by massage_pgprot().

However, this makes it very challenging to set bits (and keep them
set) if your bit is being filtered out by massage_pgprot().

This moves the bit filtering out of pfn_pte() and friends.  For
users of PAGE_KERNEL*, filtering will be done automatically inside
those macros but for users of __PAGE_KERNEL*, they need to do their
own filtering now.

Note that we also just move pfn_pte/pmd/pud() over to check_pgprot()
instead of massage_pgprot().  This way, we still *look* for
unsupported bits and properly warn about them if we find them.  This
might happen if an unfiltered __PAGE_KERNEL* value was passed in,
for instance.

- printk format warning fix from: Arnd Bergmann <arnd@arndb.de>
- boot crash fix from:            Tom Lendacky <thomas.lendacky@amd.com>
- crash bisected by:              Mike Galbraith <efault@gmx.de>

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reported-and-fixed-by: Arnd Bergmann <arnd@arndb.de>
Fixed-by: Tom Lendacky <thomas.lendacky@amd.com>
Bisected-by: Mike Galbraith <efault@gmx.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Kees Cook <keescook@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nadav Amit <namit@vmware.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20180406205509.77E1D7F6@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 22 insertions, 5 deletions

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 89d5c8886c85..5f49b4ff0c24 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -526,22 +526,39 @@ static inline pgprotval_t massage_pgprot(pgprot_t pgprot)
 	return protval;
 }
 
+static inline pgprotval_t check_pgprot(pgprot_t pgprot)
+{
+	pgprotval_t massaged_val = massage_pgprot(pgprot);
+
+	/* mmdebug.h can not be included here because of dependencies */
+#ifdef CONFIG_DEBUG_VM
+	WARN_ONCE(pgprot_val(pgprot) != massaged_val,
+		  "attempted to set unsupported pgprot: %016llx "
+		  "bits: %016llx supported: %016llx\n",
+		  (u64)pgprot_val(pgprot),
+		  (u64)pgprot_val(pgprot) ^ massaged_val,
+		  (u64)__supported_pte_mask);
+#endif
+
+	return massaged_val;
+}
+
 static inline pte_t pfn_pte(unsigned long page_nr, pgprot_t pgprot)
 {
 	return __pte(((phys_addr_t)page_nr << PAGE_SHIFT) |
-		     massage_pgprot(pgprot));
+		     check_pgprot(pgprot));
 }
 
 static inline pmd_t pfn_pmd(unsigned long page_nr, pgprot_t pgprot)
 {
 	return __pmd(((phys_addr_t)page_nr << PAGE_SHIFT) |
-		     massage_pgprot(pgprot));
+		     check_pgprot(pgprot));
 }
 
 static inline pud_t pfn_pud(unsigned long page_nr, pgprot_t pgprot)
 {
 	return __pud(((phys_addr_t)page_nr << PAGE_SHIFT) |
-		     massage_pgprot(pgprot));
+		     check_pgprot(pgprot));
 }
 
 static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
@@ -553,7 +570,7 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
 	 * the newprot (if present):
 	 */
 	val &= _PAGE_CHG_MASK;
-	val |= massage_pgprot(newprot) & ~_PAGE_CHG_MASK;
+	val |= check_pgprot(newprot) & ~_PAGE_CHG_MASK;
 
 	return __pte(val);
 }
@@ -563,7 +580,7 @@ static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
 	pmdval_t val = pmd_val(pmd);
 
 	val &= _HPAGE_CHG_MASK;
-	val |= massage_pgprot(newprot) & ~_HPAGE_CHG_MASK;
+	val |= check_pgprot(newprot) & ~_HPAGE_CHG_MASK;
 
 	return __pmd(val);
 }