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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>
This commit is contained in:
Heiko Carstens 2012-10-01 16:18:46 +02:00 committed by Martin Schwidefsky
parent 378b1e7a80
commit 5b1ba9e30c
1 changed files with 25 additions and 12 deletions
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37
arch/s390/mm/pageattr.c
View File

@ -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);