Re: [PATCH] mm/vmalloc: Take vmap_purge_lock in shrinker

[Baoquan He]

On 04/13/26 at 09:26pm, Uladzislau Rezki (Sony) wrote:
> decay_va_pool_node() can be invoked concurrently from two paths:
> __purge_vmap_area_lazy() when pools are being purged, and the
> shrinker via vmap_node_shrink_scan().
> 
> However, decay_va_pool_node() is not safe to run concurrently,
> and the shrinker path currently lacks serialization, leading
> to races and possible leaks.
> 
> Protect decay_va_pool_node() by taking vmap_purge_lock in the
> shrinker path to ensure serialization with purge users.
> 
> Cc: stable@xxxxxxxxxxxxxxx
> Cc: chenyichong <chenyichong@xxxxxxxxxxxxx>
> Fixes: 7679ba6b36db ("mm: vmalloc: add a shrinker to drain vmap pools")
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
> ---
>  mm/vmalloc.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 61caa55a4402..676851d5cfe7 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -5416,6 +5416,7 @@ vmap_node_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
>  {
>  	struct vmap_node *vn;
>  
> +	guard(mutex)(&vmap_purge_lock);
>  	for_each_vmap_node(vn)
>  		decay_va_pool_node(vn, true);

LGTM,

Reviewed-by: Baoquan He <baoquan.he@xxxxxxxxx>