From patchwork Sun May 16 04:00:17 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Madhavan T. Venkataraman" X-Patchwork-Id: 12260151 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=-17.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 82063C433B4 for ; Sun, 16 May 2021 04:04:43 +0000 (UTC) Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 01C0660C3E for ; Sun, 16 May 2021 04:04:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 01C0660C3E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.microsoft.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=desiato.20200630; h=Sender:Content-Transfer-Encoding :Content-Type:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To:Message-Id:Date: Subject:To:From:Reply-To:Cc:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=5SYq6iROLh1qjsqH/vN6MA/4BnHgGHqiMQfoeHfk9SA=; b=SD0yYFROlilaSy0PWebR8UsKE kv2eES5jklmRqKn5aqriEvRI+RXPL0lg0PsMLXsNNxvc9YZCK0+ZlBuajLHqwkqdwDG0UobjmM+LG YKZDEyhDmIL8xVsGgERX4NbWRj1dIflO6Xv/qE9U3xoPewMnf+ljPw9lkwglsIooXgmB9zwmPWZXw G25qko08XjRc48vTO4cjdQv8pEofBMOa3RJADxgm0IyS0NTBEphazS8TLA4zu5ddhH1u4X9esJuwc 8XM5ioz0WOAFEeeKzWkR90d3bg/QJ0zRK/Bqio7CQb90nO2xlsp326i8w6RKw/5sQ9H9IvPRcfLPv p2jGGY4Fw==; Received: from localhost ([::1] helo=desiato.infradead.org) by desiato.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1li7yC-00BVxR-6O; Sun, 16 May 2021 04:01:37 +0000 Received: from bombadil.infradead.org ([2607:7c80:54:e::133]) by desiato.infradead.org with esmtps (Exim 4.94 #2 (Red Hat Linux)) id 1li7xF-00BVuW-M6 for linux-arm-kernel@desiato.infradead.org; Sun, 16 May 2021 04:00:53 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:To:From:Sender: Reply-To:Cc:Content-Type:Content-ID:Content-Description; bh=Dz0YnSe+6/RNJMKZ7AszyCNm1xp4eykmTR9aH7S0FJM=; b=OqAbHIaPdwFvU9JVJrmtJTnQLc FZMtj53kMfyU8FAQTBdWEs5+8t/xaX2UJ2/dXhdbHV7nn/0ThASAMqD29k82IEs58VJOkxZ8JEQH5 zjO7+wGDXivb60ntumGYZyESAjlPTOmgNjuz1dCn7Ow0sVSCnakDceO7sxuZItcOgfy1uhheptOjr jhnB6Qf9LGlopkllyAQd5GXTRrAeExx3ISRSW7xNi2BuI1jRfZ2XjWGlLwWb3PcMhRWzC2GG4DEDF cZr4QRrcdHCvN5sJiGjxsSKXrRbgGSDnsRCoQcVvi29kqu5BEe1GXnNWJkSw+Z7TOxSiXICrcqifJ D4lW4Cdw==; Received: from linux.microsoft.com ([13.77.154.182]) by bombadil.infradead.org with esmtp (Exim 4.94 #2 (Red Hat Linux)) id 1li7xC-00ClH2-7W for linux-arm-kernel@lists.infradead.org; Sun, 16 May 2021 04:00:36 +0000 Received: from x64host.home (unknown [47.187.223.33]) by linux.microsoft.com (Postfix) with ESMTPSA id 2268D20B8006; Sat, 15 May 2021 21:00:31 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 2268D20B8006 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1621137631; bh=Dz0YnSe+6/RNJMKZ7AszyCNm1xp4eykmTR9aH7S0FJM=; h=From:To:Subject:Date:In-Reply-To:References:From; b=GMcyFxcaYX8ZIE/ZdYxSnasZZUTSox1Yci1qO2nQ0UCupX+ELPZ0SlrCDCRYatm/P Uhnr0/CQ4XpcpDqdPYkTi8409gaYkAyjnZ5JD46jYu+l8819HSsKvUmqRabYYGvXrv E5YnBY7/oax0DrIUMFBa82d/SJv9xw/vxZqiU9mo= From: madvenka@linux.microsoft.com To: broonie@kernel.org, mark.rutland@arm.com, jpoimboe@redhat.com, ardb@kernel.org, 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 v4 1/2] arm64: Introduce stack trace reliability checks in the unwinder Date: Sat, 15 May 2021 23:00:17 -0500 Message-Id: <20210516040018.128105-2-madvenka@linux.microsoft.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210516040018.128105-1-madvenka@linux.microsoft.com> References: <68eeda61b3e9579d65698a884b26c8632025e503> <20210516040018.128105-1-madvenka@linux.microsoft.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210515_210034_395583_FF903AB3 X-CRM114-Status: GOOD ( 19.02 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.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 is not a valid kernel text address, consider the stack trace unreliable. It could be some generated code. 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 | 35 ++++++++++++++++++++++++----- 2 files changed, 34 insertions(+), 5 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..d38232cab3ee 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -44,21 +44,29 @@ 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; - if (fp & 0xf) + if (fp & 0xf) { + frame->reliable = false; return -EINVAL; + } if (!tsk) tsk = current; - if (!on_accessible_stack(tsk, fp, &info)) + if (!on_accessible_stack(tsk, fp, &info)) { + frame->reliable = false; return -EINVAL; + } - if (test_bit(info.type, frame->stacks_done)) + if (test_bit(info.type, frame->stacks_done)) { + frame->reliable = false; return -EINVAL; + } /* * As stacks grow downward, any valid record on the same stack must be @@ -74,8 +82,10 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) * stack. */ if (info.type == frame->prev_type) { - if (fp <= frame->prev_fp) + if (fp <= frame->prev_fp) { + frame->reliable = false; return -EINVAL; + } } else { set_bit(frame->prev_type, frame->stacks_done); } @@ -100,14 +110,29 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) * So replace it to an original value. */ ret_stack = ftrace_graph_get_ret_stack(tsk, frame->graph++); - if (WARN_ON_ONCE(!ret_stack)) + if (WARN_ON_ONCE(!ret_stack)) { + frame->reliable = false; return -EINVAL; + } frame->pc = ret_stack->ret; } #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ frame->pc = ptrauth_strip_insn_pac(frame->pc); + /* + * Check the return PC for conditions that make unwinding unreliable. + * In each case, mark the stack trace as such. + */ + + /* + * 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. + */ + if (!__kernel_text_address(frame->pc)) + frame->reliable = false; + return 0; } NOKPROBE_SYMBOL(unwind_frame);