Patch "ARM: 8578/1: mm: ensure pmd_present only checks the valid bit" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

ARM: 8578/1: mm: ensure pmd_present only checks the valid bit

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:

     arm-8578-1-mm-ensure-pmd_present-only-checks-the-valid-bit.patch

and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Will Deacon <[email protected]>
Date: Tue, 7 Jun 2016 17:57:54 +0100
Subject: ARM: 8578/1: mm: ensure pmd_present only checks the valid bit

From: Will Deacon <[email protected]>

commit 624531886987f0f1b5d01fb598034d039198e090 upstream.

In a subsequent patch, pmd_mknotpresent will clear the valid bit of the pmd entry, resulting in a not-present entry from the hardware's perspective. Unfortunately, pmd_present simply checks for a non-zero pmd value and will therefore continue to return true even after a pmd_mknotpresent operation. Since pmd_mknotpresent is only used for managing huge entries, this is only an issue for the 3-level case.

This patch fixes the 3-level pmd_present implementation to take into account the valid bit. For bisectability, the change is made before the fix to pmd_mknotpresent.

[[email protected]: comment update regarding pmd_mknotpresent patch]

---
 arch/arm/include/asm/pgtable-2level.h |    1 +
 arch/arm/include/asm/pgtable-3level.h |    1 +
 arch/arm/include/asm/pgtable.h        |    1 -
 3 files changed, 2 insertions(+), 1 deletion(-)

@@ -193,6 +193,7 @@ static inline pmd_t *pmd_offset(pud_t *p
 
 #define pmd_large(pmd)		(pmd_val(pmd) & 2)
 #define pmd_bad(pmd)		(pmd_val(pmd) & 2)
+#define pmd_present(pmd)	(pmd_val(pmd))
 
 #define copy_pmd(pmdpd,pmdps)		\
 	do {				\

@@ -212,6 +212,7 @@ static inline pmd_t *pmd_offset(pud_t *p
 						: !!(pmd_val(pmd) & (val)))
 #define pmd_isclear(pmd, val)	(!(pmd_val(pmd) & (val)))
 
+#define pmd_present(pmd)	(pmd_isset((pmd), L_PMD_SECT_VALID))
 #define pmd_young(pmd)		(pmd_isset((pmd), PMD_SECT_AF))
 #define pte_special(pte)	(pte_isset((pte), L_PTE_SPECIAL))
 static inline pte_t pte_mkspecial(pte_t pte)

@@ -182,7 +182,6 @@ extern pgd_t swapper_pg_dir[PTRS_PER_PGD
 #define pgd_offset_k(addr)	pgd_offset(&init_mm, addr)
 
 #define pmd_none(pmd)		(!pmd_val(pmd))
-#define pmd_present(pmd)	(pmd_val(pmd))
 
 static inline pte_t *pmd_page_vaddr(pmd_t pmd)
 {

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/arm-8578-1-mm-ensure-pmd_present-only-checks-the-valid-bit.patch queue-4.4/locking-qspinlock-fix-spin_unlock_wait-some-more.patch queue-4.4/arm-8579-1-mm-fix-definition-of-pmd_mknotpresent.patch