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>

diff --git a/mm/mmap.c b/mm/mmap.c
index 84cb4b1df4a200f668a3f25da3ca726a1c780c7a..ac348ae933ba2500d72be1863c085e7597674674 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1393,11 +1393,11 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 
        /* Find the first overlapping VMA */
        vma = vma_find(&vmi, end);
+       init_vma_munmap(&vms, &vmi, vma, addr, end, uf, /* unlock = */ false);
        if (vma) {
                mt_init_flags(&mt_detach, vmi.mas.tree->ma_flags & MT_FLAGS_LOCK_MASK);
                mt_on_stack(mt_detach);
                mas_init(&mas_detach, &mt_detach, /* addr = */ 0);
-               init_vma_munmap(&vms, &vmi, vma, addr, end, uf, /* unlock = */ false);
                /* Prepare to unmap any existing mapping in the area */
                error = vms_gather_munmap_vmas(&vms, &mas_detach);
                if (error)

diff --git a/mm/vma.h b/mm/vma.h
index e78b24d1cf83cee354523ba16f85a41e30c6c6d6..0e214bbf443e6db47b5765c0af91e9dde85e37be 100644 (file)
--- 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;