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

Uladzislau Rezki
2026-04-02T15:45:52Z

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@syzkaller.appspotmail.com
> 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@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);
> }
>
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