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=-16.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 E05D3C4320A for ; Mon, 23 Aug 2021 18:58:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B9CD7613A7 for ; Mon, 23 Aug 2021 18:58:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230511AbhHWS7f (ORCPT ); Mon, 23 Aug 2021 14:59:35 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:39080 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230326AbhHWS7b (ORCPT ); Mon, 23 Aug 2021 14:59:31 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1629745128; 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=4KsO9Qxu+JAmNlNRhsiLrneXeOvaGNDskJ2+66Tdpps=; b=Ba9fTalOurSZ/qt6DEsM9wtnafySdPPPSD/tNWwObvhhfOx71hd3ciH4W9Nomr/syxdiQz YEK05t0giq7kmYmxeJiLjorXXMo2M80tfzBAHrgjT9dDGcT+dWG8cS96cM88k4KxcXaMJe gQ2J+U+eVhmGJV7+WF1aPZKu7hBXxnQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-588-CTOJFMGjNLeypaAzPYr29A-1; Mon, 23 Aug 2021 14:58:47 -0400 X-MC-Unique: CTOJFMGjNLeypaAzPYr29A-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2CBC41008075; Mon, 23 Aug 2021 18:58:46 +0000 (UTC) Received: from localhost (unknown [10.22.32.130]) by smtp.corp.redhat.com (Postfix) with ESMTP id ABE1E5D9D3; Mon, 23 Aug 2021 18:58:41 +0000 (UTC) Date: Mon, 23 Aug 2021 14:58:41 -0400 From: Eduardo Habkost To: Vitaly Kuznetsov Cc: kvm@vger.kernel.org, Paolo Bonzini , Sean Christopherson , Wanpeng Li , Jim Mattson , "Dr. David Alan Gilbert" , Nitesh Narayan Lal , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 4/4] KVM: x86: Fix stack-out-of-bounds memory access from ioapic_write_indirect() Message-ID: <20210823185841.ov7ejn2thwebcwqk@habkost.net> References: <20210823143028.649818-1-vkuznets@redhat.com> <20210823143028.649818-5-vkuznets@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210823143028.649818-5-vkuznets@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 23, 2021 at 04:30:28PM +0200, Vitaly Kuznetsov wrote: > KASAN reports the following issue: > > BUG: KASAN: stack-out-of-bounds in kvm_make_vcpus_request_mask+0x174/0x440 [kvm] > Read of size 8 at addr ffffc9001364f638 by task qemu-kvm/4798 > > CPU: 0 PID: 4798 Comm: qemu-kvm Tainted: G X --------- --- > Hardware name: AMD Corporation DAYTONA_X/DAYTONA_X, BIOS RYM0081C 07/13/2020 > Call Trace: > dump_stack+0xa5/0xe6 > print_address_description.constprop.0+0x18/0x130 > ? kvm_make_vcpus_request_mask+0x174/0x440 [kvm] > __kasan_report.cold+0x7f/0x114 > ? kvm_make_vcpus_request_mask+0x174/0x440 [kvm] > kasan_report+0x38/0x50 > kasan_check_range+0xf5/0x1d0 > kvm_make_vcpus_request_mask+0x174/0x440 [kvm] > kvm_make_scan_ioapic_request_mask+0x84/0xc0 [kvm] > ? kvm_arch_exit+0x110/0x110 [kvm] > ? sched_clock+0x5/0x10 > ioapic_write_indirect+0x59f/0x9e0 [kvm] > ? static_obj+0xc0/0xc0 > ? __lock_acquired+0x1d2/0x8c0 > ? kvm_ioapic_eoi_inject_work+0x120/0x120 [kvm] > > The problem appears to be that 'vcpu_bitmap' is allocated as a single long > on stack and it should really be KVM_MAX_VCPUS long. We also seem to clear > the lower 16 bits of it with bitmap_zero() for no particular reason (my > guess would be that 'bitmap' and 'vcpu_bitmap' variables in > kvm_bitmap_or_dest_vcpus() caused the confusion: while the later is indeed > 16-bit long, the later should accommodate all possible vCPUs). > > Fixes: 7ee30bc132c6 ("KVM: x86: deliver KVM IOAPIC scan request to target vCPUs") > Fixes: 9a2ae9f6b6bb ("KVM: x86: Zero the IOAPIC scan request dest vCPUs bitmap") > Reported-by: Dr. David Alan Gilbert > Signed-off-by: Vitaly Kuznetsov > --- > arch/x86/kvm/ioapic.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c > index ff005fe738a4..92cd4b02e9ba 100644 > --- a/arch/x86/kvm/ioapic.c > +++ b/arch/x86/kvm/ioapic.c > @@ -319,7 +319,7 @@ static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val) > unsigned index; > bool mask_before, mask_after; > union kvm_ioapic_redirect_entry *e; > - unsigned long vcpu_bitmap; > + unsigned long vcpu_bitmap[BITS_TO_LONGS(KVM_MAX_VCPUS)]; Is there a way to avoid this KVM_MAX_VCPUS-sized variable on the stack? This might hit us back when we increase KVM_MAX_VCPUS to a few thousand VCPUs (I was planning to submit a patch for that soon). > int old_remote_irr, old_delivery_status, old_dest_id, old_dest_mode; > > switch (ioapic->ioregsel) { > @@ -384,9 +384,9 @@ static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val) > irq.shorthand = APIC_DEST_NOSHORT; > irq.dest_id = e->fields.dest_id; > irq.msi_redir_hint = false; > - bitmap_zero(&vcpu_bitmap, 16); > + bitmap_zero(vcpu_bitmap, KVM_MAX_VCPUS); > kvm_bitmap_or_dest_vcpus(ioapic->kvm, &irq, > - &vcpu_bitmap); > + vcpu_bitmap); > if (old_dest_mode != e->fields.dest_mode || > old_dest_id != e->fields.dest_id) { > /* > @@ -399,10 +399,10 @@ static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val) > kvm_lapic_irq_dest_mode( > !!e->fields.dest_mode); > kvm_bitmap_or_dest_vcpus(ioapic->kvm, &irq, > - &vcpu_bitmap); > + vcpu_bitmap); > } > kvm_make_scan_ioapic_request_mask(ioapic->kvm, > - &vcpu_bitmap); > + vcpu_bitmap); > } else { > kvm_make_scan_ioapic_request(ioapic->kvm); > } > -- > 2.31.1 > -- Eduardo