mm/vmalloc: take vmap_purge_lock in shrinker

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.

Link: https://lore.kernel.org/20260413192646.14683-1-urezki@gmail.com
Fixes: 7679ba6b36db ("mm: vmalloc: add a shrinker to drain vmap pools")
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: Baoquan He <baoquan.he@linux.dev>
Cc: chenyichong <chenyichong@uniontech.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 61caa55a44027b4f09796b0f21d36430b9b8f2d5..676851d5cfe77147c95b77b5dd521ae41dfede1e 100644 (file)
--- 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);