From 5b1ba9e30cf0e259450da19189811eb140733f83 Mon Sep 17 00:00:00 2001
From: Heiko Carstens <heiko.carstens@de.ibm.com>
Date: Mon, 1 Oct 2012 16:18:46 +0200
Subject: [PATCH] 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>
---
arch/s390/mm/pageattr.c | 37 +++++++++++++++++++++++++------------
1 file changed, 25 insertions(+), 12 deletions(-)
diff --git a/arch/s390/mm/pageattr.c b/arch/s390/mm/pageattr.c
index 0f33bab3e9848..b56953dd95f82 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);
--
GitLab