From: Heiko Carstens <heiko.carstens@de.ibm.com>
Date: Mon, 1 Oct 2012 14:18:46 +0000 (+0200)
Subject: s390/mm,pageattr: add more page table walk sanity checks
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=5b1ba9e30cf0e259450da19189811eb140733f83;p=GitHub%2FLineageOS%2Fandroid_kernel_samsung_universal7580.git

s390/mm,pageattr: add more page table walk sanity checks

The current page table walk code in pageattr.c only checks for large pages
while walking the kernel page table, but happily assumes that everything
else is just fine.
Add more checks so we never access invalid memory regions.

Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
---

diff --git a/arch/s390/mm/pageattr.c b/arch/s390/mm/pageattr.c
index 0f33bab3e98..b56953dd95f 100644
--- a/arch/s390/mm/pageattr.c
+++ b/arch/s390/mm/pageattr.c
@@ -8,25 +8,38 @@
 #include <asm/cacheflush.h>
 #include <asm/pgtable.h>
 
+static pte_t *walk_page_table(unsigned long addr)
+{
+	pgd_t *pgdp;
+	pud_t *pudp;
+	pmd_t *pmdp;
+	pte_t *ptep;
+
+	pgdp = pgd_offset_k(addr);
+	if (pgd_none(*pgdp))
+		return NULL;
+	pudp = pud_offset(pgdp, addr);
+	if (pud_none(*pudp))
+		return NULL;
+	pmdp = pmd_offset(pudp, addr);
+	if (pmd_none(*pmdp) || pmd_large(*pmdp))
+		return NULL;
+	ptep = pte_offset_kernel(pmdp, addr);
+	if (pte_none(*ptep))
+		return NULL;
+	return ptep;
+}
+
 static void change_page_attr(unsigned long addr, int numpages,
 			     pte_t (*set) (pte_t))
 {
 	pte_t *ptep, pte;
-	pmd_t *pmdp;
-	pud_t *pudp;
-	pgd_t *pgdp;
 	int i;
 
 	for (i = 0; i < numpages; i++) {
-		pgdp = pgd_offset(&init_mm, addr);
-		pudp = pud_offset(pgdp, addr);
-		pmdp = pmd_offset(pudp, addr);
-		if (pmd_large(*pmdp)) {
-			WARN_ON_ONCE(1);
-			continue;
-		}
-		ptep = pte_offset_kernel(pmdp, addr);
-
+		ptep = walk_page_table(addr);
+		if (WARN_ON_ONCE(!ptep))
+			break;
 		pte = *ptep;
 		pte = set(pte);
 		__ptep_ipte(addr, ptep);