[PATCH] lock PTE before updating it in 440/BookE page fault handler

Fix 44x and BookE page fault handler to correctly lock PTE before
trying to pte_update() it, otherwise this PTE might be swapped out
after pte_present() check but before pte_uptdate() call, resulting in
corrupted PTE. This can happen with enabled preemption and low memory
condition.

Signed-off-by: Eugene Surovegin <ebs@ebshome.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
index d296eb6b4545..90628601fac7 100644
--- a/arch/powerpc/mm/pgtable_32.c
+++ b/arch/powerpc/mm/pgtable_32.c
@@ -372,7 +372,7 @@ void __init io_block_mapping(unsigned long virt, phys_addr_t phys,
  * the PTE pointer is unmodified if PTE is not found.
  */
 int
-get_pteptr(struct mm_struct *mm, unsigned long addr, pte_t **ptep)
+get_pteptr(struct mm_struct *mm, unsigned long addr, pte_t **ptep, pmd_t **pmdp)
 {
         pgd_t   *pgd;
         pmd_t   *pmd;
@@ -387,6 +387,8 @@ get_pteptr(struct mm_struct *mm, unsigned long addr, pte_t **ptep)
                         if (pte) {
                                 retval = 1;
                                 *ptep = pte;
+                                if (pmdp)
+                                        *pmdp = pmd;
                                 /* XXX caller needs to do pte_unmap, yuck */
                         }
                 }
@@ -424,7 +426,7 @@ unsigned long iopa(unsigned long addr)
                 mm = &init_mm;
 
         pa = 0;
-        if (get_pteptr(mm, addr, &pte)) {
+        if (get_pteptr(mm, addr, &pte, NULL)) {
                 pa = (pte_val(*pte) & PAGE_MASK) | (addr & ~PAGE_MASK);
                 pte_unmap(pte);
         }