mm: do not initialize TLB stack vma's with vma_init()

Commit 2c4541e24c55 ("mm: use vma_init() to initialize VMAs on stack and
data segments") tried to initialize various left-over ad-hoc vma's
"properly", but actually made things worse for the temporary vma's used
for TLB flushing.

vma_init() doesn't actually initialize all of the vma, just a few
fields, so doing something like

   -       struct vm_area_struct vma = { .vm_mm = tlb->mm, };
   +       struct vm_area_struct vma;
   +
   +       vma_init(&vma, tlb->mm);

was actually very bad: instead of having a nicely initialized vma with
every field but "vm_mm" zeroed, you'd have an entirely uninitialized vma
with only a couple of fields initialized.  And they weren't even fields
that the code in question mostly cared about.

The flush_tlb_range() function takes a "struct vma" rather than a
"struct mm_struct", because a few architectures actually care about what
kind of range it is - being able to only do an ITLB flush if it's a
range that doesn't have data accesses enabled, for example.  And all the
normal users already have the vma for doing the range invalidation.

But a few people want to call flush_tlb_range() with a range they just
made up, so they also end up using a made-up vma.  x86 just has a
special "flush_tlb_mm_range()" function for this, but other
architectures (arm and ia64) do the "use fake vma" thing instead, and
thus got caught up in the vma_init() changes.

At the same time, the TLB flushing code really doesn't care about most
other fields in the vma, so vma_init() is just unnecessary and
pointless.

This fixes things by having an explicit "this is just an initializer for
the TLB flush" initializer macro, which is used by the arm/arm64/ia64
people who mis-use this interface with just a dummy vma.

Fixes: 2c4541e24c55 ("mm: use vma_init() to initialize VMAs on stack and data segments")
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

5 files changed, 12 insertions, 17 deletions

diff --git a/arch/arm/mach-rpc/ecard.c b/arch/arm/mach-rpc/ecard.c
index 8db62cc54a6a..04b2f22c2739 100644
--- a/arch/arm/mach-rpc/ecard.c
+++ b/arch/arm/mach-rpc/ecard.c
@@ -212,7 +212,7 @@ static DEFINE_MUTEX(ecard_mutex);
  */
 static void ecard_init_pgtables(struct mm_struct *mm)
 {
-        struct vm_area_struct vma;
+        struct vm_area_struct vma = TLB_FLUSH_VMA(mm, VM_EXEC);
 
         /* We want to set up the page tables for the following mapping:
          *  Virtual     Physical
@@ -237,9 +237,6 @@ static void ecard_init_pgtables(struct mm_struct *mm)
 
         memcpy(dst_pgd, src_pgd, sizeof(pgd_t) * (EASI_SIZE / PGDIR_SIZE));
 
-        vma_init(&vma, mm);
-        vma.vm_flags = VM_EXEC;
-
         flush_tlb_range(&vma, IO_START, IO_START + IO_SIZE);
         flush_tlb_range(&vma, EASI_START, EASI_START + EASI_SIZE);
 }
diff --git a/arch/arm64/include/asm/tlb.h b/arch/arm64/include/asm/tlb.h
index d87f2d646caa..0ad1cf233470 100644
--- a/arch/arm64/include/asm/tlb.h
+++ b/arch/arm64/include/asm/tlb.h
@@ -37,9 +37,7 @@ static inline void __tlb_remove_table(void *_table)
 
 static inline void tlb_flush(struct mmu_gather *tlb)
 {
-        struct vm_area_struct vma;
-
-        vma_init(&vma, tlb->mm);
+        struct vm_area_struct vma = TLB_FLUSH_VMA(tlb->mm, 0);
 
         /*
          * The ASID allocator will either invalidate the ASID or mark
diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index 1854e49aa18a..192b3ba07075 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -108,13 +108,10 @@ static pte_t get_clear_flush(struct mm_struct *mm,
                              unsigned long pgsize,
                              unsigned long ncontig)
 {
-        struct vm_area_struct vma;
         pte_t orig_pte = huge_ptep_get(ptep);
         bool valid = pte_valid(orig_pte);
         unsigned long i, saddr = addr;
 
-        vma_init(&vma, mm);
-
         for (i = 0; i < ncontig; i++, addr += pgsize, ptep++) {
                 pte_t pte = ptep_get_and_clear(mm, addr, ptep);
 
@@ -127,8 +124,10 @@ static pte_t get_clear_flush(struct mm_struct *mm,
                         orig_pte = pte_mkdirty(orig_pte);
         }
 
-        if (valid)
+        if (valid) {
+                struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0);
                 flush_tlb_range(&vma, saddr, addr);
+        }
         return orig_pte;
 }
 
@@ -147,10 +146,9 @@ static void clear_flush(struct mm_struct *mm,
                              unsigned long pgsize,
                              unsigned long ncontig)
 {
-        struct vm_area_struct vma;
+        struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0);
         unsigned long i, saddr = addr;
 
-        vma_init(&vma, mm);
         for (i = 0; i < ncontig; i++, addr += pgsize, ptep++)
                 pte_clear(mm, addr, ptep);
 
diff --git a/arch/ia64/include/asm/tlb.h b/arch/ia64/include/asm/tlb.h
index db89e7306081..516355a774bf 100644
--- a/arch/ia64/include/asm/tlb.h
+++ b/arch/ia64/include/asm/tlb.h
@@ -115,12 +115,11 @@ ia64_tlb_flush_mmu_tlbonly(struct mmu_gather *tlb, unsigned long start, unsigned
                 flush_tlb_all();
         } else {
                 /*
-                 * XXX fix me: flush_tlb_range() should take an mm pointer instead of a
-                 * vma pointer.
+                 * flush_tlb_range() takes a vma instead of a mm pointer because
+                 * some architectures want the vm_flags for ITLB/DTLB flush.
                  */
-                struct vm_area_struct vma;
+                struct vm_area_struct vma = TLB_FLUSH_VMA(tlb->mm, 0);
 
-                vma_init(&vma, tlb->mm);
                 /* flush the address range from the tlb: */
                 flush_tlb_range(&vma, start, end);
                 /* now flush the virt. page-table area mapping the address range: */
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7ba6d356d18f..68a5121694ef 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -466,6 +466,9 @@ static inline void vma_set_anonymous(struct vm_area_struct *vma)
         vma->vm_ops = NULL;
 }
 
+/* flush_tlb_range() takes a vma, not a mm, and can care about flags */
+#define TLB_FLUSH_VMA(mm,flags) { .vm_mm = (mm), .vm_flags = (flags) }
+
 struct mmu_gather;
 struct inode;