From patchwork Thu Jul 29 14:08:27 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 12408865 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=-19.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 30564C4320E for ; Thu, 29 Jul 2021 14:09:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 113B760F4A for ; Thu, 29 Jul 2021 14:09:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238828AbhG2OJw (ORCPT ); Thu, 29 Jul 2021 10:09:52 -0400 Received: from mail.kernel.org ([198.145.29.99]:57696 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239273AbhG2OIe (ORCPT ); Thu, 29 Jul 2021 10:08:34 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 6988160EBD; Thu, 29 Jul 2021 14:08:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1627567711; bh=vq57kfNtne2ZkfDVHujGhteCErzVm2gfEbZS/xIziG0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=XLMbrB4eu2drRAND/GawjjdIsMTGPygolb0EjGDiV0c5gS7O2b86O3CFHzr/M4gMw 6R12o+bHFvpwNkE00L/aTWoq0USgGmN0UlBasYupTfc8r8oE9kLYBCS0Eid9i1vIaB ZICg9WeYbh+MP53uxThmfWmBsKidi7BYp8dMk7rNM2YVd34m9lMq/qZyXI4xYeIa1a O/9tbLRpBY081EvuJdn5UlPGPzCR+vWt7mRNVSAX0V/r7LiheFTzE5z+CfMHxq+5XL 28T0fmv0gfRHGe8MgX+yBVMtHA5LScYhlsD3JR8eC5tit1ASX9VvnUNtL0rb+zy/f4 tQkAy2Fm2cJag== From: Masami Hiramatsu To: Steven Rostedt , Josh Poimboeuf , Ingo Molnar Cc: X86 ML , Masami Hiramatsu , Daniel Xu , linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kuba@kernel.org, mingo@redhat.com, ast@kernel.org, Thomas Gleixner , Borislav Petkov , Peter Zijlstra , kernel-team@fb.com, yhs@fb.com, linux-ia64@vger.kernel.org, Abhishek Sagar , Andrii Nakryiko Subject: [PATCH -tip v10 16/16] x86/kprobes: Fixup return address in generic trampoline handler Date: Thu, 29 Jul 2021 23:08:27 +0900 Message-Id: <162756770686.301564.6919347996726334805.stgit@devnote2> X-Mailer: git-send-email 2.25.1 In-Reply-To: <162756755600.301564.4957591913842010341.stgit@devnote2> References: <162756755600.301564.4957591913842010341.stgit@devnote2> User-Agent: StGit/0.19 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org In x86, the fake return address on the stack saved by __kretprobe_trampoline() will be replaced with the real return address after returning from trampoline_handler(). Before fixing the return address, the real return address can be found in the 'current->kretprobe_instances'. However, since there is a window between updating the 'current->kretprobe_instances' and fixing the address on the stack, if an interrupt happens at that timing and the interrupt handler does stacktrace, it may fail to unwind because it can not get the correct return address from 'current->kretprobe_instances'. This will eliminate that window by fixing the return address right before updating 'current->kretprobe_instances'. Signed-off-by: Masami Hiramatsu Tested-by: Andrii Nakryiko --- Changes in v9: - Fixes the changelog. This can eliminate the window. - Add more comment how it works. Changes in v7: - Add a prototype for arch_kretprobe_fixup_return() --- arch/x86/kernel/kprobes/core.c | 18 ++++++++++++++++-- include/linux/kprobes.h | 3 +++ kernel/kprobes.c | 11 +++++++++++ 3 files changed, 30 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index 7e1111c19605..fce99e249d61 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -1065,6 +1065,16 @@ NOKPROBE_SYMBOL(__kretprobe_trampoline); */ STACK_FRAME_NON_STANDARD_FP(__kretprobe_trampoline); +/* This is called from kretprobe_trampoline_handler(). */ +void arch_kretprobe_fixup_return(struct pt_regs *regs, + kprobe_opcode_t *correct_ret_addr) +{ + unsigned long *frame_pointer = ®s->sp + 1; + + /* Replace fake return address with real one. */ + *frame_pointer = (unsigned long)correct_ret_addr; +} + /* * Called from __kretprobe_trampoline */ @@ -1082,8 +1092,12 @@ __used __visible void trampoline_handler(struct pt_regs *regs) regs->sp += sizeof(long); frame_pointer = ®s->sp + 1; - /* Replace fake return address with real one. */ - *frame_pointer = kretprobe_trampoline_handler(regs, frame_pointer); + /* + * The return address at 'frame_pointer' is recovered by the + * arch_kretprobe_fixup_return() which called from the + * kretprobe_trampoline_handler(). + */ + kretprobe_trampoline_handler(regs, frame_pointer); /* * Copy FLAGS to 'pt_regs::sp' so that __kretprobe_trapmoline() diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h index 6d47a9da1e0a..e974caf39d3e 100644 --- a/include/linux/kprobes.h +++ b/include/linux/kprobes.h @@ -188,6 +188,9 @@ extern void arch_prepare_kretprobe(struct kretprobe_instance *ri, struct pt_regs *regs); extern int arch_trampoline_kprobe(struct kprobe *p); +void arch_kretprobe_fixup_return(struct pt_regs *regs, + kprobe_opcode_t *correct_ret_addr); + void __kretprobe_trampoline(void); /* * Since some architecture uses structured function pointer, diff --git a/kernel/kprobes.c b/kernel/kprobes.c index ebc587b9a346..b62af9fc3607 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -1922,6 +1922,15 @@ unsigned long kretprobe_find_ret_addr(struct task_struct *tsk, void *fp, } NOKPROBE_SYMBOL(kretprobe_find_ret_addr); +void __weak arch_kretprobe_fixup_return(struct pt_regs *regs, + kprobe_opcode_t *correct_ret_addr) +{ + /* + * Do nothing by default. Please fill this to update the fake return + * address on the stack with the correct one on each arch if possible. + */ +} + unsigned long __kretprobe_trampoline_handler(struct pt_regs *regs, void *frame_pointer) { @@ -1967,6 +1976,8 @@ unsigned long __kretprobe_trampoline_handler(struct pt_regs *regs, first = first->next; } + arch_kretprobe_fixup_return(regs, correct_ret_addr); + /* Unlink all nodes for this frame. */ first = current->kretprobe_instances.first; current->kretprobe_instances.first = node->next;