lkml.org 
[lkml]   [2008]   [May]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [git head] X86_PAT & mprotect
On Fri, May 09, 2008 at 01:05:19PM -0700, Venki Pallipadi wrote:
> On Fri, May 09, 2008 at 12:08:18PM +0200, Ingo Molnar wrote:
> >
> > * Venki Pallipadi <venkatesh.pallipadi@intel.com> wrote:
> >
> > > > I've tried doing it slightly differently below, don't know whether
> > > > you'll consider it an improvement or not.
> > >
> > > Hugh: Thanks for looking into this. Yes. I like your modified patch.
> > > Simpler and smaller.
> >
> > i have stuck your original patch into testing and nothing blew up so
> > far. Due to the mm/ bits this is not for the scope of x86.git, but
> > obviously it all looks good and is .26-worthy to me:
> >
> > Acked-by: Ingo Molnar <mingo@elte.hu>
> > Tested-by: Ingo Molnar <mingo@elte.hu>
> >
> > Venki, could you please send a full patch against -git that has
> > everything from Hugh included, with an updated changelog, for
> > Linus/Andrew to ack/apply?
> >
>
> Ingo,
>
> Split up the patch into two parts as the pci part was unrelated to mprotect
> problem in a sense.

And the second patch for mprotect problem.


There is a defect in mprotect, which lets the user to 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>

---
include/asm-x86/pgtable.h | 16 +++++++++++++---
mm/mprotect.c | 11 ++++++++++-
2 files changed, 23 insertions(+), 4 deletions(-)

Index: linux-2.6/mm/mprotect.c
===================================================================
--- linux-2.6.orig/mm/mprotect.c 2008-05-09 10:50:28.000000000 -0700
+++ linux-2.6/mm/mprotect.c 2008-05-09 11:01:23.000000000 -0700
@@ -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;
Index: linux-2.6/include/asm-x86/pgtable.h
===================================================================
--- linux-2.6.orig/include/asm-x86/pgtable.h 2008-05-09 10:50:28.000000000 -0700
+++ linux-2.6/include/asm-x86/pgtable.h 2008-05-09 11:01:23.000000000 -0700
@@ -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
* 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)

\
 
 \ /
  Last update: 2008-05-09 22:11    [W:1.071 / U:0.712 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site