[PATCH] always check if !vma

[Lorenzo Stoakes]

We perform VMA lookup in a couple more places which, in theory, can
unexpectedly fail to find a VMA.

In these cases, correctly indicate failure.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-lkp/202503101328.442cc724-lkp@xxxxxxxxx
---
 mm/mremap.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/mm/mremap.c b/mm/mremap.c
index 0ab0c88072a0..af022e3b89e2 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -1066,10 +1066,13 @@ static unsigned long shrink_vma(struct vma_remap_struct *vrm,
 	 * replace the invalidated VMA with the one that may have now been
 	 * split.
 	 */
-	if (drop_lock)
+	if (drop_lock) {
 		vrm->mmap_locked = false;
-	else
+	} else {
 		vrm->vma = vma_lookup(mm, vrm->addr);
+		if (!vrm->vma)
+			return -EFAULT;
+	}

 	return 0;
 }
@@ -1108,6 +1111,8 @@ static unsigned long mremap_to(struct vma_remap_struct *vrm)
 		 * this can invalidate the old VMA. Reset.
 		 */
 		vrm->vma = vma_lookup(mm, vrm->addr);
+		if (!vrm->vma)
+			return -EFAULT;
 	}

 	if (vrm->remap_type == MREMAP_SHRINK) {
--
2.48.1