From: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Subject: kasan: don't tag stacks allocated with pagealloc Patch series "kasan: support stack instrumentation for tag-based mode", v2. This patch (of 5): Prepare Software Tag-Based KASAN for stack tagging support. With Tag-Based KASAN when kernel stacks are allocated via pagealloc (which happens when CONFIG_VMAP_STACK is not enabled), they get tagged. KASAN instrumentation doesn't expect the sp register to be tagged, and this leads to false-positive reports. Fix by resetting the tag of kernel stack pointers after allocation. Link: http://lkml.kernel.org/r/cover.1596199677.git.andreyknvl@xxxxxxxxxx Link: http://lkml.kernel.org/r/cover.1596544734.git.andreyknvl@xxxxxxxxxx Link: http://lkml.kernel.org/r/12d8c678869268dd0884b01271ab592f30792abf.1596544734.git.andreyknvl@xxxxxxxxxx Link: http://lkml.kernel.org/r/01c678b877755bcf29009176592402cdf6f2cb15.1596199677.git.andreyknvl@xxxxxxxxxx Link: https://bugzilla.kernel.org/show_bug.cgi?id=203497 Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> Cc: Alexander Potapenko <glider@xxxxxxxxxx> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Marco Elver <elver@xxxxxxxxxx> Cc: Walter Wu <walter-zh.wu@xxxxxxxxxxxx> Cc: Elena Petrova <lenaptr@xxxxxxxxxx> Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx> Cc: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Ard Biesheuvel <ardb@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/fork.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/kernel/fork.c~kasan-dont-tag-stacks-allocated-with-pagealloc +++ a/kernel/fork.c @@ -261,7 +261,7 @@ static unsigned long *alloc_thread_stack THREAD_SIZE_ORDER); if (likely(page)) { - tsk->stack = page_address(page); + tsk->stack = kasan_reset_tag(page_address(page)); return tsk->stack; } return NULL; @@ -302,6 +302,7 @@ static unsigned long *alloc_thread_stack { unsigned long *stack; stack = kmem_cache_alloc_node(thread_stack_cache, THREADINFO_GFP, node); + stack = kasan_reset_tag(stack); tsk->stack = stack; return stack; } _
