Messages in this thread Patch in this message | | | Date | Fri, 9 May 2008 13:09:30 -0700 | From | Venki Pallipadi <> | Subject | Re: [git head] X86_PAT & mprotect |
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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)
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