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

[Uladzislau Rezki]

On Thu, Apr 02, 2026 at 04:14:13PM +0800, Qing Wang 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@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://syzkaller.appspot.com/bug?extid=37b7f6cd519f7fb8d32a
>
I can not access two above links. Are they valid? I would like to have
a look at report.

> Signed-off-by: Qing Wang <wangqing7171@xxxxxxxxx>
> ---
>  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);
>  	}
>
va->list does not require to be initialized. Because:

	spin_lock(&vn->busy.lock);
	insert_vmap_area(va, &vn->busy.root, &vn->busy.head);
	spin_unlock(&vn->busy.lock);

when a node is inserted into list_head, its next/prev pointers are
properly set by the list_add().

Or, am i missing something?

--
Uladzislau Rezki