The stack pointer always uses the match-all tag, so MTE never checks tags on stack accesses. Tagging stack memory on every thread creation is pure overhead. - Pass __GFP_SKIP_KASAN in gfp_mask for vmalloc-backed stacks so the vmalloc path skips HW tag setup (see previous patch). - For the cached VMAP reuse path, skip kasan_unpoison_range() when HW tags are enabled since the memory will only be accessed through the match-all tagged SP. - For the normal page allocator path, pass __GFP_SKIP_KASAN directly to the page allocator. Signed-off-by: Muhammad Usama Anjum --- kernel/fork.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/kernel/fork.c b/kernel/fork.c index bb0c2613a5604..2baf4db39b5a4 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -345,7 +345,8 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node) } /* Reset stack metadata. */ - kasan_unpoison_range(vm_area->addr, THREAD_SIZE); + if (!kasan_hw_tags_enabled()) + kasan_unpoison_range(vm_area->addr, THREAD_SIZE); stack = kasan_reset_tag(vm_area->addr); @@ -358,7 +359,7 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node) } stack = __vmalloc_node(THREAD_SIZE, THREAD_ALIGN, - GFP_VMAP_STACK, + GFP_VMAP_STACK | __GFP_SKIP_KASAN, node, __builtin_return_address(0)); if (!stack) return -ENOMEM; @@ -410,7 +411,8 @@ static void thread_stack_delayed_free(struct task_struct *tsk) static int alloc_thread_stack_node(struct task_struct *tsk, int node) { - struct page *page = alloc_pages_node(node, THREADINFO_GFP, + struct page *page = alloc_pages_node(node, + THREADINFO_GFP | __GFP_SKIP_KASAN, THREAD_SIZE_ORDER); if (likely(page)) { -- 2.47.3