From 51fb34de2a4c8fa0f221246313700bfe3b6c586d Mon Sep 17 00:00:00 2001 From: Andrey Konovalov Date: Thu, 24 Mar 2022 18:11:10 -0700 Subject: kasan, arm64: reset pointer tags of vmapped stacks Once tag-based KASAN modes start tagging vmalloc() allocations, kernel stacks start getting tagged if CONFIG_VMAP_STACK is enabled. Reset the tag of kernel stack pointers after allocation in arch_alloc_vmap_stack(). For SW_TAGS KASAN, when CONFIG_KASAN_STACK is enabled, the instrumentation can't handle the SP register being tagged. For HW_TAGS KASAN, there's no instrumentation-related issues. However, the impact of having a tagged SP register needs to be properly evaluated, so keep it non-tagged for now. Note, that the memory for the stack allocation still gets tagged to catch vmalloc-into-stack out-of-bounds accesses. [andreyknvl@google.com: fix case when a stack is retrieved from cached_stacks] Link: https://lkml.kernel.org/r/f50c5f96ef896d7936192c888b0c0a7674e33184.1644943792.git.andreyknvl@google.com [dan.carpenter@oracle.com: remove unnecessary check in alloc_thread_stack_node()] Link: https://lkml.kernel.org/r/20220301080706.GB17208@kili Link: https://lkml.kernel.org/r/698c5ab21743c796d46c15d075b9481825973e34.1643047180.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov Signed-off-by: Dan Carpenter Acked-by: Catalin Marinas Acked-by: Marco Elver Reviewed-by: Marco Elver Cc: Alexander Potapenko Cc: Andrey Ryabinin Cc: Dmitry Vyukov Cc: Evgenii Stepanov Cc: Mark Rutland Cc: Peter Collingbourne Cc: Vincenzo Frascino Cc: Will Deacon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/fork.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) (limited to 'kernel') diff --git a/kernel/fork.c b/kernel/fork.c index ce0ffe48937f..9796897560ab 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -286,11 +286,13 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node) if (!s) continue; - /* Mark stack accessible for KASAN. */ + /* Reset stack metadata. */ kasan_unpoison_range(s->addr, THREAD_SIZE); + stack = kasan_reset_tag(s->addr); + /* Clear stale pointers from reused stack. */ - memset(s->addr, 0, THREAD_SIZE); + memset(stack, 0, THREAD_SIZE); if (memcg_charge_kernel_stack(s)) { vfree(s->addr); @@ -298,7 +300,7 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node) } tsk->stack_vm_area = s; - tsk->stack = s->addr; + tsk->stack = stack; return 0; } @@ -326,8 +328,7 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node) * so cache the vm_struct. */ tsk->stack_vm_area = vm; - if (stack) - stack = kasan_reset_tag(stack); + stack = kasan_reset_tag(stack); tsk->stack = stack; return 0; } -- cgit v1.2.3