Re: [PATCH] mm/vmalloc: fix KMSAN uninit-value warning in decay_va_pool_node()

[Uladzislau Rezki <urezki@gmail.com>]

Hello, Qing Wang!

Let me check it close!

On Thu, Apr 2, 2026 at 10:14 AM Qing Wang <wangqing7171@gmail.com> wrote:
>
> KMSAN reported an uninit-value warning when accessing vmap_area->list
> in decay_va_pool_node():
>
>   BUG: KMSAN: uninit-value in __list_del_entry_valid include/linux/list.h:-1 [inline]
>   BUG: KMSAN: uninit-value in __list_del_entry include/linux/list.h:223 [inline]
>   BUG: KMSAN: uninit-value in list_del_init include/linux/list.h:295 [inline]
>   BUG: KMSAN: uninit-value in decay_va_pool_node+0xf78/0x1dd0 mm/vmalloc.c:2255
>
>   Uninit was created at:
>    kmem_cache_alloc_node_noprof+0x3cd/0x12d0 mm/slub.c:4918
>    alloc_vmap_area+0x327/0x2e30 mm/vmalloc.c:2065
>
> The root cause is that if node_alloc() fail and the va is allocated via
> kmem_cache_alloc_node() by alloc_vmap_area(), va->list will be uninitialized.
>
> Fix this by explicitly initializing va->list after allocation.
>
> Reported-by: syzbot+37b7f6cd519f7fb8d32a@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=37b7f6cd519f7fb8d32a
> Signed-off-by: Qing Wang <wangqing7171@gmail.com>
> ---
>  mm/vmalloc.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 61caa55a4402..8aebbb51e178 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2071,6 +2071,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
>                  * to avoid false negatives.
>                  */
>                 kmemleak_scan_area(&va->rb_node, SIZE_MAX, gfp_mask);
> +               INIT_LIST_HEAD(&va->list);
>         }
>
>  retry:
> --
> 2.34.1
>


-- 
Uladzislau Rezki