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 15203C433EF for ; Fri, 13 May 2022 11:10:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1379780AbiEMLKO (ORCPT ); Fri, 13 May 2022 07:10:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43216 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1379733AbiEMLKL (ORCPT ); Fri, 13 May 2022 07:10:11 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AF9DA2A5E9D for ; Fri, 13 May 2022 04:10:08 -0700 (PDT) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1652440207; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=D8KLHqVQtCIkBNwToZ5fdFqQrvPlxGtB7EqGxkiaVLg=; b=C3YN/lpNIatUZ1jSSajMzf8gAKJjdczxnx1vlBtduen8gZaEhL29kev4HdGFUyDDvmj2SQ OPPtRtr5bGyQQhMdvgQSYFoniI5Lvka974v9oieFM1oeVonF8VAT/KsZcJoVWltQy+E3qR vxx8khx/ECbgI+gtIJPilEx2lPigvSjqklAiKc6Crj0ywjx0GN3l0AyMx5LG5b5/8w9CeT HrBkK6m45vUChJ1JeBEMEmOvd4AQ4Y8jlJ0pS7CQ41NB6ozQUkYATZ252ShRuckKokICIn TY4zP1UjhDrU7qyxDg48KFFyo9S1NsZhj3IzBFNkS3Pj50OhQXltGQRx8SxFAw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1652440207; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=D8KLHqVQtCIkBNwToZ5fdFqQrvPlxGtB7EqGxkiaVLg=; b=8/Q5H2F71NRtRscbCKIedtWvnXfCIPftVKtCvXBUsGHfV2qlGD9eajiPVRiVlkskqt83v8 8mQ7GrqQHWBjcDAg== To: Sean Christopherson , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org Cc: "H. Peter Anvin" , linux-kernel@vger.kernel.org, "Guilherme G . Piccoli" , Vitaly Kuznetsov , Paolo Bonzini , Sean Christopherson Subject: [PATCH] x86/nmi: Make register_nmi_handler() more robust In-Reply-To: <20220511234332.3654455-1-seanjc@google.com> References: <20220511234332.3654455-1-seanjc@google.com> Date: Fri, 13 May 2022 13:10:06 +0200 Message-ID: <87zgjlsn75.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org register_nmi_handler() has no sanity check whether a handler has been registered already. Such an unintended double-add leads to list corruption and hard to diagnose problems during the next NMI handling. Init the list head in the static nmi action struct and check it for being empty in register_nmi_handler(). Reported-by: Sean Christopherson Signed-off-by: Thomas Gleixner --- arch/x86/include/asm/nmi.h | 1 + arch/x86/kernel/nmi.c | 10 +++++++--- 2 files changed, 8 insertions(+), 3 deletions(-) --- a/arch/x86/include/asm/nmi.h +++ b/arch/x86/include/asm/nmi.h @@ -47,6 +47,7 @@ struct nmiaction { #define register_nmi_handler(t, fn, fg, n, init...) \ ({ \ static struct nmiaction init fn##_na = { \ + .list = LIST_HEAD_INIT(fn##_na.list), \ .handler = (fn), \ .name = (n), \ .flags = (fg), \ --- a/arch/x86/kernel/nmi.c +++ b/arch/x86/kernel/nmi.c @@ -157,7 +157,7 @@ int __register_nmi_handler(unsigned int struct nmi_desc *desc = nmi_to_desc(type); unsigned long flags; - if (!action->handler) + if (WARN_ON_ONCE(action->handler || !list_empty(&action->list))) return -EINVAL; raw_spin_lock_irqsave(&desc->lock, flags); @@ -186,7 +186,7 @@ EXPORT_SYMBOL(__register_nmi_handler); void unregister_nmi_handler(unsigned int type, const char *name) { struct nmi_desc *desc = nmi_to_desc(type); - struct nmiaction *n; + struct nmiaction *n, *found = NULL; unsigned long flags; raw_spin_lock_irqsave(&desc->lock, flags); @@ -200,12 +200,16 @@ void unregister_nmi_handler(unsigned int WARN(in_nmi(), "Trying to free NMI (%s) from NMI context!\n", n->name); list_del_rcu(&n->list); + found = n; break; } } raw_spin_unlock_irqrestore(&desc->lock, flags); - synchronize_rcu(); + if (found) { + synchronize_rcu(); + INIT_LIST_HEAD(found); + } } EXPORT_SYMBOL_GPL(unregister_nmi_handler);