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mprotect: prevent alteration of the PAT bits

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There is a defect in mprotect, which lets the user change the page cache
type bits by-passing the kernel reserve_memtype and free_memtype
wrappers.  Fix the problem by not letting mprotect change the PAT bits.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Venki Pallipadi 2008-05-14 16:05:51 -07:00 committed by Linus Torvalds
parent 44c81433e8
commit 1c12c4cf94
2 changed files with 23 additions and 4 deletions
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16
include/asm-x86/pgtable.h
View File

@ -57,7 +57,8 @@
#define _KERNPG_TABLE (_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED | \
_PAGE_DIRTY)
#define _PAGE_CHG_MASK (PTE_MASK | _PAGE_ACCESSED | _PAGE_DIRTY)
#define _PAGE_CHG_MASK (PTE_MASK | _PAGE_PCD | _PAGE_PWT | \
_PAGE_ACCESSED | _PAGE_DIRTY)
#define _PAGE_CACHE_MASK (_PAGE_PCD | _PAGE_PWT)
#define _PAGE_CACHE_WB (0)
@ -288,12 +289,21 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
* Chop off the NX bit (if present), and add the NX portion of
* the newprot (if present):
*/
val &= _PAGE_CHG_MASK & ~_PAGE_NX;
val |= pgprot_val(newprot) & __supported_pte_mask;
val &= _PAGE_CHG_MASK;
val |= pgprot_val(newprot) & (~_PAGE_CHG_MASK) & __supported_pte_mask;
return __pte(val);
}
/* mprotect needs to preserve PAT bits when updating vm_page_prot */
#define pgprot_modify pgprot_modify
static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
{
pgprotval_t preservebits = pgprot_val(oldprot) & _PAGE_CHG_MASK;
pgprotval_t addbits = pgprot_val(newprot);
return __pgprot(preservebits | addbits);
}
#define pte_pgprot(x) __pgprot(pte_val(x) & (0xfff | _PAGE_NX))
#define canon_pgprot(p) __pgprot(pgprot_val(p) & __supported_pte_mask)

11
mm/mprotect.c
View File

@ -26,6 +26,13 @@
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>
#ifndef pgprot_modify
static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
{
return newprot;
}
#endif
static void change_pte_range(struct mm_struct *mm, pmd_t *pmd,
unsigned long addr, unsigned long end, pgprot_t newprot,
int dirty_accountable)
@ -192,7 +199,9 @@ success:
* held in write mode.
*/
vma->vm_flags = newflags;
vma->vm_page_prot = vm_get_page_prot(newflags);
vma->vm_page_prot = pgprot_modify(vma->vm_page_prot,
vm_get_page_prot(newflags));
if (vma_wants_writenotify(vma)) {
vma->vm_page_prot = vm_get_page_prot(newflags & ~VM_SHARED);
dirty_accountable = 1;