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 X-Spam-Level: X-Spam-Status: No, score=-26.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT, USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C0E09C433B4 for ; Mon, 3 May 2021 17:36:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 85FAF610A6 for ; Mon, 3 May 2021 17:36:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231407AbhECRhX (ORCPT ); Mon, 3 May 2021 13:37:23 -0400 Received: from linux.microsoft.com ([13.77.154.182]:54486 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231378AbhECRhS (ORCPT ); Mon, 3 May 2021 13:37:18 -0400 Received: from x64host.home (unknown [47.187.223.33]) by linux.microsoft.com (Postfix) with ESMTPSA id F400B20B8006; Mon, 3 May 2021 10:36:23 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com F400B20B8006 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1620063384; bh=27H+BvFer3s1Y37vngYKoBI/y9wscqHm39MmyAoxw0U=; h=From:To:Subject:Date:In-Reply-To:References:From; b=dl6V/Uswvh85+qjvxPyvO12cWqKGTHC7p2cooPOwG26LmWMxATKi/fYBN53tScEXR 1mhyM3FpBIYEpnthksh7zyag6o50NOTInqXXOS+BFbhMwN40GRdJA/denkOBcnikNf WGxKCP2a75rmSDeUb6UPt6EdYGgAM7nKWerpV8pc= From: madvenka@linux.microsoft.com To: broonie@kernel.org, jpoimboe@redhat.com, mark.rutland@arm.com, jthierry@redhat.com, catalin.marinas@arm.com, will@kernel.org, jmorris@namei.org, pasha.tatashin@soleen.com, linux-arm-kernel@lists.infradead.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, madvenka@linux.microsoft.com Subject: [RFC PATCH v3 1/4] arm64: Introduce stack trace reliability checks in the unwinder Date: Mon, 3 May 2021 12:36:12 -0500 Message-Id: <20210503173615.21576-2-madvenka@linux.microsoft.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210503173615.21576-1-madvenka@linux.microsoft.com> References: <65cf4dfbc439b010b50a0c46ec500432acde86d6> <20210503173615.21576-1-madvenka@linux.microsoft.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Madhavan T. Venkataraman" The unwinder should check for the presence of various features and conditions that can render the stack trace unreliable and mark the the stack trace as unreliable for the benefit of the caller. Introduce the first reliability check - If a return PC encountered in a stack trace is not a valid kernel text address, the stack trace is considered unreliable. It could be some generated code. Mark the stack trace unreliable. Other reliability checks will be added in the future. Signed-off-by: Madhavan T. Venkataraman --- arch/arm64/include/asm/stacktrace.h | 4 ++++ arch/arm64/kernel/stacktrace.c | 19 ++++++++++++++++--- 2 files changed, 20 insertions(+), 3 deletions(-) diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h index eb29b1fe8255..f1eab6b029f7 100644 --- a/arch/arm64/include/asm/stacktrace.h +++ b/arch/arm64/include/asm/stacktrace.h @@ -49,6 +49,8 @@ struct stack_info { * * @graph: When FUNCTION_GRAPH_TRACER is selected, holds the index of a * replacement lr value in the ftrace graph stack. + * + * @reliable: Is this stack frame reliable? */ struct stackframe { unsigned long fp; @@ -59,6 +61,7 @@ struct stackframe { #ifdef CONFIG_FUNCTION_GRAPH_TRACER int graph; #endif + bool reliable; }; extern int unwind_frame(struct task_struct *tsk, struct stackframe *frame); @@ -169,6 +172,7 @@ static inline void start_backtrace(struct stackframe *frame, bitmap_zero(frame->stacks_done, __NR_STACK_TYPES); frame->prev_fp = 0; frame->prev_type = STACK_TYPE_UNKNOWN; + frame->reliable = true; } #endif /* __ASM_STACKTRACE_H */ diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index d55bdfb7789c..c21a1bca28f3 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -44,6 +44,8 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) unsigned long fp = frame->fp; struct stack_info info; + frame->reliable = true; + /* Terminal record; nothing to unwind */ if (!fp) return -ENOENT; @@ -86,12 +88,24 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) */ frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp)); frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8)); + frame->pc = ptrauth_strip_insn_pac(frame->pc); frame->prev_fp = fp; frame->prev_type = info.type; + /* + * First, make sure that the return address is a proper kernel text + * address. A NULL or invalid return address probably means there's + * some generated code which __kernel_text_address() doesn't know + * about. Mark the stack trace as not reliable. + */ + if (!__kernel_text_address(frame->pc)) { + frame->reliable = false; + return 0; + } + #ifdef CONFIG_FUNCTION_GRAPH_TRACER if (tsk->ret_stack && - (ptrauth_strip_insn_pac(frame->pc) == (unsigned long)return_to_handler)) { + frame->pc == (unsigned long)return_to_handler) { struct ftrace_ret_stack *ret_stack; /* * This is a case where function graph tracer has @@ -103,11 +117,10 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) if (WARN_ON_ONCE(!ret_stack)) return -EINVAL; frame->pc = ret_stack->ret; + frame->pc = ptrauth_strip_insn_pac(frame->pc); } #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ - frame->pc = ptrauth_strip_insn_pac(frame->pc); - return 0; } NOKPROBE_SYMBOL(unwind_frame); -- 2.25.1