[RFC,01/11] mm/mremap: fix dup_anon_vma() in vma_merge() case 4

Commit Message

Vlastimil Babka Feb. 24, 2023, 10 a.m. UTC

In case 4, we are shrinking 'prev' (PPPP in the comment) and expanding
'mid' (NNNN). So we need to make sure 'mid' clones the anon_vma from
'prev', if it doesn't have any. After commit 0503ea8f5ba7 ("mm/mmap:
remove __vma_adjust()") we can fail to do that due to wrong parameters
for dup_anon_vma(). The call is a no-op because res == next, adjust ==
mid and mid == next. Fix it.

Fixes: 0503ea8f5ba7 ("mm/mmap: remove __vma_adjust()")
Signed-off-by: Vlastimil Babka <[e-mail]>
---
 mm/mmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Patch

diff --git a/mm/mmap.c b/mm/mmap.c
index 20f21f0949dd..740b54be3ed4 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -973,7 +973,7 @@  struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
 			vma_end = addr;
 			adjust = mid;
 			adj_next = -(vma->vm_end - addr);
-			err = dup_anon_vma(res, adjust);
+			err = dup_anon_vma(adjust, prev);
 		} else {
 			vma = next;			/* case 3 */
 			vma_start = addr;