mm: Fix TLB flush for not-first PFNMAP mappings in unmap_region()

This is a stable-specific patch.
I botched the stable-specific rewrite of
commit b67fbebd4cf98 ("mmu_gather: Force tlb-flush VM_PFNMAP vmas"):
As Hugh pointed out, unmap_region() actually operates on a list of VMAs,
and the variable "vma" merely points to the first VMA in that list.
So if we want to check whether any of the VMAs we're operating on is
PFNMAP or MIXEDMAP, we have to iterate through the list and check each VMA.

Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/mm/mmap.c b/mm/mmap.c
index a696c17ba9b0d27f24b897b59db3cae44af96711..3e1e23d5e67a6aa5927848d43504441fdccc8631 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2524,6 +2524,7 @@ static void unmap_region(struct mm_struct *mm,
 {
        struct vm_area_struct *next = prev ? prev->vm_next : mm->mmap;
        struct mmu_gather tlb;
+       struct vm_area_struct *cur_vma;
 
        lru_add_drain();
        tlb_gather_mmu(&tlb, mm, start, end);
@@ -2538,8 +2539,12 @@ static void unmap_region(struct mm_struct *mm,
         * concurrent flush in this region has to be coming through the rmap,
         * and we synchronize against that using the rmap lock.
         */
-       if ((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) != 0)
-               tlb_flush_mmu(&tlb);
+       for (cur_vma = vma; cur_vma; cur_vma = cur_vma->vm_next) {
+               if ((cur_vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) != 0) {
+                       tlb_flush_mmu(&tlb);
+                       break;
+               }
+       }
 
        free_pgtables(&tlb, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
                                 next ? next->vm_start : USER_PGTABLES_CEILING);