From mboxrd@z Thu Jan 1 00:00:00 1970 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 9E1D5C38A02 for ; Sun, 30 Oct 2022 12:55:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229819AbiJ3MzD (ORCPT ); Sun, 30 Oct 2022 08:55:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46916 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229441AbiJ3MzB (ORCPT ); Sun, 30 Oct 2022 08:55:01 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DC8CAC23 for ; Sun, 30 Oct 2022 05:55:00 -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 ams.source.kernel.org (Postfix) with ESMTPS id 61C61B80D34 for ; Sun, 30 Oct 2022 12:54:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8DECBC433D6; Sun, 30 Oct 2022 12:54:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1667134498; bh=5yoWTKKzJPGZvHI5RJZ+Ao+F3Il25e1XFouqIcbN/OM=; h=From:To:Cc:Subject:Date:From; b=HxNVdgXEvFeRh1kbN198L/t6hi9jKHlgNeKv2l+40ZteX0YlwXW+eGG6VM/fFMq7w 31+NuSwyxTfZtVkel46cbH7T4tSLoFyxYrbZrYXniVgUImPkSKnasv1W3KVRfl5sn/ 19AvicBwhny8xHgsgFcXmFKAu2KjdH+T+ylsvqkCNGjfC8+0KsrzAbt/UoPOzRO5QT JCzSf5oYfswN0PXMmBnMv+lQhm53ydqMiaXesMm7QCYbCI+/VzqUIgTPG4LwiGdaVg mtIQToo8nIiOaxlUaiuRIfvSG2FyXSpdJr1XFI3/L8NrN2iC2kZO/li7P96IyNyNbQ N8RRKe1TQSujw== From: Jisheng Zhang To: Paul Walmsley , Palmer Dabbelt , Albert Ou , Guo Ren Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v3] riscv: fix race when vmap stack overflow Date: Sun, 30 Oct 2022 20:45:17 +0800 Message-Id: <20221030124517.2370-1-jszhang@kernel.org> X-Mailer: git-send-email 2.37.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 v2: - use REG_AMOSWAP - add comment to the purpose of smp_store_release() Since v1: - use smp_store_release directly - use unsigned int instead of atomic_t arch/riscv/include/asm/asm.h | 1 + arch/riscv/kernel/entry.S | 4 ++++ arch/riscv/kernel/traps.c | 9 +++++++++ 3 files changed, 14 insertions(+) diff --git a/arch/riscv/include/asm/asm.h b/arch/riscv/include/asm/asm.h index 1b471ff73178..acf563072b8b 100644 --- a/arch/riscv/include/asm/asm.h +++ b/arch/riscv/include/asm/asm.h @@ -23,6 +23,7 @@ #define REG_L __REG_SEL(ld, lw) #define REG_S __REG_SEL(sd, sw) #define REG_SC __REG_SEL(sc.d, sc.w) +#define REG_AMOSWAP __REG_SEL(amoswap.d, amoswap.w) #define REG_ASM __REG_SEL(.dword, .word) #define SZREG __REG_SEL(8, 4) #define LGREG __REG_SEL(3, 2) diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S index b9eda3fcbd6d..ea6b78dac739 100644 --- a/arch/riscv/kernel/entry.S +++ b/arch/riscv/kernel/entry.S @@ -404,6 +404,10 @@ handle_syscall_trace_exit: #ifdef CONFIG_VMAP_STACK handle_kernel_stack_overflow: +1: la sp, spin_shadow_stack + REG_AMOSWAP sp, sp, (sp) + bnez sp, 1b + la sp, shadow_stack addi sp, sp, SHADOW_OVERFLOW_STACK_SIZE diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c index f3e96d60a2ff..dea47f329708 100644 --- a/arch/riscv/kernel/traps.c +++ b/arch/riscv/kernel/traps.c @@ -221,11 +221,20 @@ asmlinkage unsigned long get_overflow_stack(void) OVERFLOW_STACK_SIZE; } +unsigned long spin_shadow_stack; + asmlinkage void handle_bad_stack(struct pt_regs *regs) { unsigned long tsk_stk = (unsigned long)current->stack; unsigned long ovf_stk = (unsigned long)this_cpu_ptr(overflow_stack); + /* + * to ensure spin flag is set after the sp is used in entry.S: + * //load per-cpu overflow stack. + * REG_L sp, -8(sp) + */ + smp_store_release(&spin_shadow_stack, 0); + console_verbose(); pr_emerg("Insufficient stack space to handle exception!\n"); -- 2.37.2