[3.13.y.z extended stable] Patch "sparc64: Add basic validations to {pud, pmd}_bad()." has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    sparc64: Add basic validations to {pud,pmd}_bad().

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.7.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From f29936f3f8f3cba4550a851249a89cebe478b9bc Mon Sep 17 00:00:00 2001
From: "David S. Miller" <davem at davemloft.net>
Date: Tue, 29 Apr 2014 13:03:27 -0700
Subject: sparc64: Add basic validations to {pud,pmd}_bad().

[ Upstream commit 26cf432551d749e7d581db33529507a711c6eaab ]

Instead of returning false we should at least check the most basic
things, otherwise page table corruptions will be very difficult to
debug.

PMD and PTE tables are of size PAGE_SIZE, so none of the sub-PAGE_SIZE
bits should be set.

We also complement this with a check that the physical address the
pud/pmd points to is valid memory.

PowerPC was used as a guide while implementating this.

Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/sparc/include/asm/pgtable_64.h | 46 +++++++++++++++++++++++++------------
 1 file changed, 31 insertions(+), 15 deletions(-)

diff --git a/arch/sparc/include/asm/pgtable_64.h b/arch/sparc/include/asm/pgtable_64.h
index 0ad0a12..baccf35 100644
--- a/arch/sparc/include/asm/pgtable_64.h
+++ b/arch/sparc/include/asm/pgtable_64.h
@@ -71,6 +71,23 @@

 #include <linux/sched.h>

+extern unsigned long sparc64_valid_addr_bitmap[];
+
+/* Needs to be defined here and not in linux/mm.h, as it is arch dependent */
+static inline bool __kern_addr_valid(unsigned long paddr)
+{
+	if ((paddr >> MAX_PHYS_ADDRESS_BITS) != 0UL)
+		return false;
+	return test_bit(paddr >> ILOG2_4MB, sparc64_valid_addr_bitmap);
+}
+
+static inline bool kern_addr_valid(unsigned long addr)
+{
+	unsigned long paddr = __pa(addr);
+
+	return __kern_addr_valid(paddr);
+}
+
 /* Entries per page directory level. */
 #define PTRS_PER_PTE	(1UL << (PAGE_SHIFT-3))
 #define PTRS_PER_PMD	(1UL << PMD_BITS)
@@ -743,6 +760,20 @@ static inline int pmd_present(pmd_t pmd)

 #define pmd_none(pmd)			(!pmd_val(pmd))

+/* pmd_bad() is only called on non-trans-huge PMDs.  Our encoding is
+ * very simple, it's just the physical address.  PTE tables are of
+ * size PAGE_SIZE so make sure the sub-PAGE_SIZE bits are clear and
+ * the top bits outside of the range of any physical address size we
+ * support are clear as well.  We also validate the physical itself.
+ */
+#define pmd_bad(pmd)			((pmd_val(pmd) & ~PAGE_MASK) || \
+					 !__kern_addr_valid(pmd_val(pmd)))
+
+#define pud_none(pud)			(!pud_val(pud))
+
+#define pud_bad(pud)			((pud_val(pud) & ~PAGE_MASK) || \
+					 !__kern_addr_valid(pud_val(pud)))
+
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 extern void set_pmd_at(struct mm_struct *mm, unsigned long addr,
 		       pmd_t *pmdp, pmd_t pmd);
@@ -776,10 +807,7 @@ static inline unsigned long __pmd_page(pmd_t pmd)
 #define pud_page_vaddr(pud)		\
 	((unsigned long) __va(pud_val(pud)))
 #define pud_page(pud) 			virt_to_page((void *)pud_page_vaddr(pud))
-#define pmd_bad(pmd)			(0)
 #define pmd_clear(pmdp)			(pmd_val(*(pmdp)) = 0UL)
-#define pud_none(pud)			(!pud_val(pud))
-#define pud_bad(pud)			(0)
 #define pud_present(pud)		(pud_val(pud) != 0U)
 #define pud_clear(pudp)			(pud_val(*(pudp)) = 0UL)

@@ -909,18 +937,6 @@ extern unsigned long pte_file(pte_t);
 extern pte_t pgoff_to_pte(unsigned long);
 #define PTE_FILE_MAX_BITS	(64UL - PAGE_SHIFT - 1UL)

-extern unsigned long sparc64_valid_addr_bitmap[];
-
-/* Needs to be defined here and not in linux/mm.h, as it is arch dependent */
-static inline bool kern_addr_valid(unsigned long addr)
-{
-	unsigned long paddr = __pa(addr);
-
-	if ((paddr >> MAX_PHYS_ADDRESS_BITS) != 0UL)
-		return false;
-	return test_bit(paddr >> ILOG2_4MB, sparc64_valid_addr_bitmap);
-}
-
 extern int page_in_phys_avail(unsigned long paddr);

 /*
--
1.9.1