From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AA4381FB7 for ; Fri, 25 Mar 2022 01:11:11 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 75D7DC340EE; Fri, 25 Mar 2022 01:11:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1648170671; bh=QNv5HjDELt9zqB7usRbJE0Lh3n1r0l/8EFCxZvOSM5Y=; h=Date:To:From:In-Reply-To:Subject:From; b=eCxjljCqhxwYN2cW4Ydx2W3V8YNSoHef5pRunUyx8QH1iWuzIE157zMoOb08HJYdI 6avEwGSfPUk8Fi2CbeEdiFiqsujW29cYLt8yA4mFbcaln4bD2Gs3AFGiJOTNXBt2Np Hfhw0hYhvY4ZE7QKnUNU5SBC/WfHn11ST6jASHFs= Date: Thu, 24 Mar 2022 18:11:10 -0700 To: will@kernel.org,vincenzo.frascino@arm.com,ryabinin.a.a@gmail.com,pcc@google.com,mark.rutland@arm.com,glider@google.com,eugenis@google.com,elver@google.com,dvyukov@google.com,dan.carpenter@oracle.com,catalin.marinas@arm.com,andreyknvl@google.com,akpm@linux-foundation.org,patches@lists.linux.dev,linux-mm@kvack.org,mm-commits@vger.kernel.org,torvalds@linux-foundation.org,akpm@linux-foundation.org From: Andrew Morton In-Reply-To: <20220324180758.96b1ac7e17675d6bc474485e@linux-foundation.org> Subject: [patch 052/114] kasan, arm64: reset pointer tags of vmapped stacks Message-Id: <20220325011111.75D7DC340EE@smtp.kernel.org> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: From: Andrey Konovalov 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 --- arch/arm64/include/asm/vmap_stack.h | 5 ++++- kernel/fork.c | 11 ++++++----- 2 files changed, 10 insertions(+), 6 deletions(-) --- a/arch/arm64/include/asm/vmap_stack.h~kasan-arm64-reset-pointer-tags-of-vmapped-stacks +++ a/arch/arm64/include/asm/vmap_stack.h @@ -17,10 +17,13 @@ */ static inline unsigned long *arch_alloc_vmap_stack(size_t stack_size, int node) { + void *p; + BUILD_BUG_ON(!IS_ENABLED(CONFIG_VMAP_STACK)); - return __vmalloc_node(stack_size, THREAD_ALIGN, THREADINFO_GFP, node, + p = __vmalloc_node(stack_size, THREAD_ALIGN, THREADINFO_GFP, node, __builtin_return_address(0)); + return kasan_reset_tag(p); } #endif /* __ASM_VMAP_STACK_H */ --- a/kernel/fork.c~kasan-arm64-reset-pointer-tags-of-vmapped-stacks +++ a/kernel/fork.c @@ -286,11 +286,13 @@ static int alloc_thread_stack_node(struc 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(struc } tsk->stack_vm_area = s; - tsk->stack = s->addr; + tsk->stack = stack; return 0; } @@ -326,8 +328,7 @@ static int alloc_thread_stack_node(struc * 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; } _