From nobody Tue Apr 7 23:39:14 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 526B8C4332F for ; Thu, 20 Oct 2022 14:43:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230198AbiJTOnP (ORCPT ); Thu, 20 Oct 2022 10:43:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35836 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229972AbiJTOnM (ORCPT ); Thu, 20 Oct 2022 10:43:12 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 22D4E1A1B28 for ; Thu, 20 Oct 2022 07:43:07 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id A07A561BC2 for ; Thu, 20 Oct 2022 14:43:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8C9F1C433C1; Thu, 20 Oct 2022 14:43:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1666276986; bh=1mkLwMduon6mFlXdZ1go1kC/+lZJsRhnP5cXjU0CP9Y=; h=From:To:Cc:Subject:Date:From; b=Se7BLwYGeyBpaIOaeMvTnpIfQPcLMy/HG8PNLOANqEHWjQO00EEcU/9jHx1e4NEcE Jrau7ya8nIOCwPX2I7qExozEfboSDqcOn/awK3TURUhTT2f2APsBtlkLkdvqmDKULG K8nwJidULg8IeFaF35l1ft1sh4gh/z4m8wFDlhPCz2zGNIq3pU3+PhEp7rainQg7Hr urKMdQLW61oxmVeixPwxqNTKEHGKvekeyHEZUzCTm5mity78SeuRqwM9TbbJbX8ghh 6gixtq4lXPVK8ApMSpbFxhJihlKxt412Cp6TsnaNX6NlkVanE1KXYkJUE6ryLVqbwV XcYIjkGmKMpFw== From: Jisheng Zhang To: Paul Walmsley , Palmer Dabbelt , Albert Ou Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Guo Ren Subject: [PATCH v2] riscv: fix race when vmap stack overflow Date: Thu, 20 Oct 2022 22:33:29 +0800 Message-Id: <20221020143329.3276-1-jszhang@kernel.org> X-Mailer: git-send-email 2.37.2 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Currently, when detecting vmap stack overflow, riscv firstly switches to the so called shadow stack, then use this shadow stack to call the get_overflow_stack() to get the overflow stack. However, there's a race here if two or more harts use the same shadow stack at the same time. To solve this race, we introduce spin_shadow_stack atomic var, which will be swap between its own address and 0 in atomic way, when the var is set, it means the shadow_stack is being used; when the var is cleared, it means the shadow_stack isn't being used. Fixes: 31da94c25aea ("riscv: add VMAP_STACK overflow detection") Signed-off-by: Jisheng Zhang Suggested-by: Guo Ren --- Since v1: - use smp_store_release directly - use unsigned int instead of atomic_t arch/riscv/kernel/entry.S | 4 ++++ arch/riscv/kernel/traps.c | 4 ++++ 2 files changed, 8 insertions(+) diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S index b9eda3fcbd6d..7b924b16792b 100644 --- a/arch/riscv/kernel/entry.S +++ b/arch/riscv/kernel/entry.S @@ -404,6 +404,10 @@ handle_syscall_trace_exit: =20 #ifdef CONFIG_VMAP_STACK handle_kernel_stack_overflow: +1: la sp, spin_shadow_stack + amoswap.w sp, sp, (sp) + bnez sp, 1b + la sp, shadow_stack addi sp, sp, SHADOW_OVERFLOW_STACK_SIZE =20 diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c index f3e96d60a2ff..f1f57c1241b6 100644 --- a/arch/riscv/kernel/traps.c +++ b/arch/riscv/kernel/traps.c @@ -221,11 +221,15 @@ asmlinkage unsigned long get_overflow_stack(void) OVERFLOW_STACK_SIZE; } =20 +unsigned int spin_shadow_stack; + asmlinkage void handle_bad_stack(struct pt_regs *regs) { unsigned long tsk_stk =3D (unsigned long)current->stack; unsigned long ovf_stk =3D (unsigned long)this_cpu_ptr(overflow_stack); =20 + smp_store_release(&spin_shadow_stack, 0); + console_verbose(); =20 pr_emerg("Insufficient stack space to handle exception!\n"); --=20 2.37.2