On Fri, Apr 29, 2022 at 8:40 AM Miaohe Lin <linmiaohe@xxxxxxxxxx> wrote:
>
> alloc_slots could fail to allocate memory under heavy memory pressure. So
> we should check zhdr->slots against NULL to avoid future null pointer
> dereferencing.
>
> Fixes: fc5488651c7d ("z3fold: simplify freeing slots")
> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> ---
> mm/z3fold.c | 12 +++++++++++-
> 1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/mm/z3fold.c b/mm/z3fold.c
> index c2260f5a5885..5d8c21f2bc59 100644
> --- a/mm/z3fold.c
> +++ b/mm/z3fold.c
> @@ -940,9 +940,19 @@ static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,
> }
> }
>
> - if (zhdr && !zhdr->slots)
> + if (zhdr && !zhdr->slots) {
> zhdr->slots = alloc_slots(pool, GFP_ATOMIC);
> + if (!zhdr->slots)
> + goto out_fail;
> + }
> return zhdr;
> +
> +out_fail:
> + if (!kref_put(&zhdr->refcount, release_z3fold_page_locked)) {
> + add_to_unbuddied(pool, zhdr);
> + z3fold_page_unlock(zhdr);
> + }
> + return NULL;
> }
Reviewed-by: Vitaly Wool <vitaly.wool@xxxxxxxxxxxx>
> /*
> --
> 2.23.0
>
