mm/vma: support vma == NULL in init_vma_munmap()

Adding support for a NULL vma means the init_vma_munmap() can be
initialized for a less error-prone process when calling
vms_complete_munmap_vmas() later on.

Link: https://lkml.kernel.org/r/20240830040101.822209-11-Liam.Howlett@oracle.com
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Bert Karwatzki <spasswolf@web.de>
Cc: Jeff Xu <jeffxu@chromium.org>
Cc: Jiri Olsa <olsajiri@gmail.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 8 insertions, 3 deletions

diff --git a/mm/vma.h b/mm/vma.h
index e78b24d1cf83..0e214bbf443e 100644
--- a/mm/vma.h
+++ b/mm/vma.h
@@ -95,9 +95,14 @@ static inline void init_vma_munmap(struct vma_munmap_struct *vms,
 {
 	vms->vmi = vmi;
 	vms->vma = vma;
-	vms->mm = vma->vm_mm;
-	vms->start = start;
-	vms->end = end;
+	if (vma) {
+		vms->mm = vma->vm_mm;
+		vms->start = start;
+		vms->end = end;
+	} else {
+		vms->mm = NULL;
+		vms->start = vms->end = 0;
+	}
 	vms->unlock = unlock;
 	vms->uf = uf;
 	vms->vma_count = 0;