[PATCH mm] mm: hugetlb: Add checks for NULL for vma returned from find_vma. find_vma may return NULL, that's why its return value is usually checked for NULL.

[Esina Ekaterina]

Found by Astra Linux on behalf of Linux Verification Center
(linuxtesting.org) with SVACE.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Esina Ekaterina <eesina@xxxxxxxxxxxxx>
---
 mm/hugetlb.c | 32 ++++++++++++++++++--------------
 1 file changed, 18 insertions(+), 14 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 3499b3803384..2162bfcf8f46 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5394,9 +5394,6 @@ void adjust_range_if_pmd_sharing_possible(struct vm_area_struct *vma,
 pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
 {
 	struct vm_area_struct *vma = find_vma(mm, addr);
-	struct address_space *mapping = vma->vm_file->f_mapping;
-	pgoff_t idx = ((addr - vma->vm_start) >> PAGE_SHIFT) +
-			vma->vm_pgoff;
 	struct vm_area_struct *svma;
 	unsigned long saddr;
 	pte_t *spte = NULL;
@@ -5406,18 +5403,25 @@ pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud)
 	if (!vma_shareable(vma, addr))
 		return (pte_t *)pmd_alloc(mm, pud, addr);
 
-	i_mmap_assert_locked(mapping);
-	vma_interval_tree_foreach(svma, &mapping->i_mmap, idx, idx) {
-		if (svma == vma)
-			continue;
+	if (vma && vma->vm_file && vm->vm_file->f_mapping
+		&& vma->vm_start && vma->vm->vm_pgoff) {
+		struct address_space *mapping = vma->vm_file->f_mapping;
+		pgoff_t idx = ((addr - vma->vm_start) >> PAGE_SHIFT) +
+			vma->vm_pgoff;
 
-		saddr = page_table_shareable(svma, vma, addr, idx);
-		if (saddr) {
-			spte = huge_pte_offset(svma->vm_mm, saddr,
-					       vma_mmu_pagesize(svma));
-			if (spte) {
-				get_page(virt_to_page(spte));
-				break;
+		i_mmap_assert_locked(mapping);
+		vma_interval_tree_foreach(svma, &mapping->i_mmap, idx, idx) {
+			if (svma == vma)
+				continue;
+
+			saddr = page_table_shareable(svma, vma, addr, idx);
+			if (saddr) {
+				spte = huge_pte_offset(svma->vm_mm, saddr,
+							vma_mmu_pagesize(svma));
+				if (spte) {
+					get_page(virt_to_page(spte));
+					break;
+				}
 			}
 		}
 	}
-- 
2.39.0