thp: prevent hugepages during args/env copying into the user stack

Transparent hugepages can only be created if rmap is fully
functional. So we must prevent hugepages to be created while
is_vma_temporary_stack() is true.

This also optmizes away some harmless but unnecessary setting of
khugepaged_scan.address and it switches some BUG_ON to VM_BUG_ON.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 18 insertions, 20 deletions

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 8e6c8c42bc3c..df29c8fde36b 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -57,7 +57,8 @@ extern pmd_t *page_check_address_pmd(struct page *page,
           (transparent_hugepage_flags &                                 \
            (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG) &&                   \
            ((__vma)->vm_flags & VM_HUGEPAGE))) &&                       \
-         !((__vma)->vm_flags & VM_NOHUGEPAGE))
+         !((__vma)->vm_flags & VM_NOHUGEPAGE) &&                        \
+         !is_vma_temporary_stack(__vma))
 #define transparent_hugepage_defrag(__vma)                              \
         ((transparent_hugepage_flags &                                  \
           (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)) ||                     \
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e62ddb8f24b6..3e29781ee762 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1811,6 +1811,8 @@ static void collapse_huge_page(struct mm_struct *mm,
         /* VM_PFNMAP vmas may have vm_ops null but vm_file set */
         if (!vma->anon_vma || vma->vm_ops || vma->vm_file)
                 goto out;
+        if (is_vma_temporary_stack(vma))
+                goto out;
         VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma));
 
         pgd = pgd_offset(mm, address);
@@ -2032,32 +2034,27 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
                 if ((!(vma->vm_flags & VM_HUGEPAGE) &&
                      !khugepaged_always()) ||
                     (vma->vm_flags & VM_NOHUGEPAGE)) {
+                skip:
                         progress++;
                         continue;
                 }
-
                 /* VM_PFNMAP vmas may have vm_ops null but vm_file set */
-                if (!vma->anon_vma || vma->vm_ops || vma->vm_file) {
-                        khugepaged_scan.address = vma->vm_end;
-                        progress++;
-                        continue;
-                }
+                if (!vma->anon_vma || vma->vm_ops || vma->vm_file)
+                        goto skip;
+                if (is_vma_temporary_stack(vma))
+                        goto skip;
+
                 VM_BUG_ON(is_linear_pfn_mapping(vma) || is_pfn_mapping(vma));
 
                 hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
                 hend = vma->vm_end & HPAGE_PMD_MASK;
-                if (hstart >= hend) {
-                        progress++;
-                        continue;
-                }
+                if (hstart >= hend)
+                        goto skip;
+                if (khugepaged_scan.address > hend)
+                        goto skip;
                 if (khugepaged_scan.address < hstart)
                         khugepaged_scan.address = hstart;
-                if (khugepaged_scan.address > hend) {
-                        khugepaged_scan.address = hend + HPAGE_PMD_SIZE;
-                        progress++;
-                        continue;
-                }
-                BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
+                VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
 
                 while (khugepaged_scan.address < hend) {
                         int ret;
@@ -2086,7 +2083,7 @@ breakouterloop:
 breakouterloop_mmap_sem:
 
         spin_lock(&khugepaged_mm_lock);
-        BUG_ON(khugepaged_scan.mm_slot != mm_slot);
+        VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
         /*
          * Release the current mm_slot if this mm is about to die, or
          * if we scanned all vmas of this mm.
@@ -2241,9 +2238,9 @@ static int khugepaged(void *none)
 
         for (;;) {
                 mutex_unlock(&khugepaged_mutex);
-                BUG_ON(khugepaged_thread != current);
+                VM_BUG_ON(khugepaged_thread != current);
                 khugepaged_loop();
-                BUG_ON(khugepaged_thread != current);
+                VM_BUG_ON(khugepaged_thread != current);
 
                 mutex_lock(&khugepaged_mutex);
                 if (!khugepaged_enabled())