[PATCH] fork: zero vmap stack using clear_pages() instead of memset()

[Linus Walleij <linusw@kernel.org>]

After the introduction of clear_pages() we exploit the
fact that the process vm_area is allocated in contiguous
pages to just clear them all in one swift operation.

Suggested-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://lore.kernel.org/linux-mm/dpnwsp7dl4535rd7qmszanw6u5an2p74uxfex4dh53frpb7pu3@2bnjjavjrepe/
Suggested-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Link: https://lore.kernel.org/20240311164638.2015063-7-pasha.tatashin@soleen.com
Signed-off-by: Linus Walleij <linusw@kernel.org>
---
 kernel/fork.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index e832da9d15a4..88d78ccef245 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -345,7 +345,7 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node)
 		stack = kasan_reset_tag(vm_area->addr);
 
 		/* Clear stale pointers from reused stack. */
-		memset(stack, 0, THREAD_SIZE);
+		clear_pages(vm_area->addr, vm_area->nr_pages);
 
 		tsk->stack_vm_area = vm_area;
 		tsk->stack = stack;

---
base-commit: 6de23f81a5e08be8fbf5e8d7e9febc72a5b5f27f
change-id: 20260224-mm-fork-clear-pages-ae7c52d12a93

Best regards,
-- 
Linus Walleij <linusw@kernel.org>