[PATCH v1 1/4] kasan: Avoid sleepable page allocation from atomic context

Alexander Gordeev
2025-04-07T15:12:03Z

apply_to_page_range() enters lazy MMU mode and then invokes
kasan_populate_vmalloc_pte() callback on each page table walk
iteration. The lazy MMU mode may only be entered only under
protection of the page table lock. However, the callback can
go into sleep when trying to allocate a single page.

Change __get_free_page() allocation mode from GFP_KERNEL to
GFP_ATOMIC to avoid scheduling out while in atomic context.

Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
---
mm/kasan/shadow.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
index 88d1c9dcb507..edfa77959474 100644
--- a/mm/kasan/shadow.c
+++ b/mm/kasan/shadow.c
@@ -301,7 +301,7 @@ static int kasan_populate_vmalloc_pte(pte_t *ptep, unsigned long addr,
if (likely(!pte_none(ptep_get(ptep))))
return 0;

- page = __get_free_page(GFP_KERNEL);
+ page = __get_free_page(GFP_ATOMIC);
if (!page)
return -ENOMEM;

--
2.45.2