On 7/20/19 1:32 AM, Ralph Campbell wrote:
> When CONFIG_MIGRATE_VMA_HELPER is enabled, migrate_vma() calls
> migrate_vma_collect() which initializes a struct mm_walk but
> didn't initialize mm_walk.pud_entry. (Found by code inspection)
> Use a C structure initialization to make sure it is set to NULL.
>
> Fixes: 8763cb45ab967 ("mm/migrate: new memory migration helper for use with
> device memory")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
> Cc: "Jérôme Glisse" <jglisse@xxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
So this bug can manifest by some garbage address on stack being called, right? I
wonder, how comes it didn't actually happen yet?
> ---
> mm/migrate.c | 17 +++++++----------
> 1 file changed, 7 insertions(+), 10 deletions(-)
>
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 515718392b24..a42858d8e00b 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -2340,16 +2340,13 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
> static void migrate_vma_collect(struct migrate_vma *migrate)
> {
> struct mmu_notifier_range range;
> - struct mm_walk mm_walk;
> -
> - mm_walk.pmd_entry = migrate_vma_collect_pmd;
> - mm_walk.pte_entry = NULL;
> - mm_walk.pte_hole = migrate_vma_collect_hole;
> - mm_walk.hugetlb_entry = NULL;
> - mm_walk.test_walk = NULL;
> - mm_walk.vma = migrate->vma;
> - mm_walk.mm = migrate->vma->vm_mm;
> - mm_walk.private = migrate;
> + struct mm_walk mm_walk = {
> + .pmd_entry = migrate_vma_collect_pmd,
> + .pte_hole = migrate_vma_collect_hole,
> + .vma = migrate->vma,
> + .mm = migrate->vma->vm_mm,
> + .private = migrate,
> + };
>
> mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm_walk.mm,
> migrate->start,
>
