From nobody Thu Apr 9 12:31:44 2026 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 863F7C4332F for ; Fri, 4 Nov 2022 18:33:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232169AbiKDSdJ (ORCPT ); Fri, 4 Nov 2022 14:33:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51946 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232138AbiKDSdA (ORCPT ); Fri, 4 Nov 2022 14:33:00 -0400 Received: from mail-pl1-x64a.google.com (mail-pl1-x64a.google.com [IPv6:2607:f8b0:4864:20::64a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DC00440919 for ; Fri, 4 Nov 2022 11:32:57 -0700 (PDT) Received: by mail-pl1-x64a.google.com with SMTP id q3-20020a17090311c300b0017898180dddso4120501plh.0 for ; Fri, 04 Nov 2022 11:32:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=YYBJ31ou5Rwg5LoGtjJ6FG68fLUfYn1uUGIk9MyRKGY=; b=lSOSZi+kphdHFzsfDzuxPltgdYT52XM9vY5sOjBzYtVo0p2a1WGY/nTF11dzy8Qbx8 ez1v5pmtsDrjYrir1duKzoEcT0qcI0g4kWaXGKHs4w1r3UM3X3tUgQ8qOZioUqbgqyeb 7RrYIa7XhuH5JbZ1TLX3yoZ5EQafu4N/7G108aQOf3w0N6ZtRs6rsuQxxcbzzUyV4ANi k6JFOVVConNg+UlCWbyXqapxwbpAty/FwQEd6zOf5bWeiAad6+ZqYsyIYEaa4vkYu6hX Baa0w3EULQ5pVyq6f0u6UOAP+cI3sAwFz9DtPeHjV3OyccRoR8qPsYvul2C9eMIqzZvr Sopw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=YYBJ31ou5Rwg5LoGtjJ6FG68fLUfYn1uUGIk9MyRKGY=; b=IIQLy2fOzY7/DV6yYfGA1YS1QXo99p3Y0I1dct5Uoeb1YbbJDFqu5CzDJz8nbVteV+ S7OgmAVq3YRD7UuxiKYCNuVKt+ZSU4Esy4cEcLBeNFjDl/WBlqdHXay7ImFz8guzMfId LJCD4P+u1N72i7JSd4CHyI3Ux2vTZkyj8sYK09J1Apz3U5jPJezmV87aJeQkQa8rcnDc 1lyuOPA/mHCCkgNSII+jMrJlS7pCX/tg5C9aA+PxxI9PsqotjZLExN4ScHk6REFZOAsj hd3m/J6WLbKpGmZn8oVLZ5Kb2BJwEkvxMNYqbGhLKRSCKCcOPp5y3F/soTPFGZ62ekdb tr4g== X-Gm-Message-State: ACrzQf1k5EB2PGGJlQc+oXTiJoomp+ihyJhiRE1DKj10jMxwwJPkdIay duoUNMLigzTdrO4YIDcy+9Y048p7x5U= X-Google-Smtp-Source: AMsMyM5AzYyUyY4WLPr0o7OeQqIFQaRG+NcbCZ2jehe2vxhaONBNiLQ0/sbFDkHT0pjDK29vN/bWCU5LarI= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a05:6a00:2886:b0:565:c4e2:2634 with SMTP id ch6-20020a056a00288600b00565c4e22634mr366477pfb.0.1667586777418; Fri, 04 Nov 2022 11:32:57 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 4 Nov 2022 18:32:47 +0000 In-Reply-To: <20221104183247.834988-1-seanjc@google.com> Mime-Version: 1.0 References: <20221104183247.834988-1-seanjc@google.com> X-Mailer: git-send-email 2.38.1.431.g37b22c650d-goog Message-ID: <20221104183247.834988-4-seanjc@google.com> Subject: [PATCH 3/3] x86/kasan: Populate shadow for shared chunk of the CPU entry area From: Sean Christopherson To: Andrey Ryabinin , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org Cc: Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Vincenzo Frascino , "H. Peter Anvin" , kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, Sean Christopherson , syzbot+8cdd16fd5a6c0565e227@syzkaller.appspotmail.com Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Popuplate the shadow for the shared portion of the CPU entry area, i.e. the read-only IDT mapping, during KASAN initialization. A recent change modified KASAN to map the per-CPU areas on-demand, but forgot to keep a shadow for the common area that is shared amongst all CPUs. Map the common area in KASAN init instead of letting idt_map_in_cea() do the dirty work so that it Just Works in the unlikely event more shared data is shoved into the CPU entry area. The bug manifests as a not-present #PF when software attempts to lookup an IDT entry, e.g. when KVM is handling IRQs on Intel CPUs (KVM performs direct CALL to the IRQ handler to avoid the overhead of INTn): BUG: unable to handle page fault for address: fffffbc0000001d8 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 16c03a067 P4D 16c03a067 PUD 0 Oops: 0000 [#1] PREEMPT SMP KASAN CPU: 5 PID: 901 Comm: repro Tainted: G W 6.1.0-rc3+ #410 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:kasan_check_range+0xdf/0x190 vmx_handle_exit_irqoff+0x152/0x290 [kvm_intel] vcpu_run+0x1d89/0x2bd0 [kvm] kvm_arch_vcpu_ioctl_run+0x3ce/0xa70 [kvm] kvm_vcpu_ioctl+0x349/0x900 [kvm] __x64_sys_ioctl+0xb8/0xf0 do_syscall_64+0x2b/0x50 entry_SYSCALL_64_after_hwframe+0x46/0xb0 Fixes: 9fd429c28073 ("x86/kasan: Map shadow for percpu pages on demand") Reported-by: syzbot+8cdd16fd5a6c0565e227@syzkaller.appspotmail.com Cc: Andrey Ryabinin Signed-off-by: Sean Christopherson --- arch/x86/mm/kasan_init_64.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c index afc5e129ca7b..0302491d799d 100644 --- a/arch/x86/mm/kasan_init_64.c +++ b/arch/x86/mm/kasan_init_64.c @@ -341,7 +341,7 @@ void __init kasan_populate_shadow_for_vaddr(void *va, s= ize_t size, int nid) =20 void __init kasan_init(void) { - unsigned long shadow_cea_begin, shadow_cea_end; + unsigned long shadow_cea_begin, shadow_cea_per_cpu_begin, shadow_cea_end; int i; =20 memcpy(early_top_pgt, init_top_pgt, sizeof(early_top_pgt)); @@ -384,6 +384,7 @@ void __init kasan_init(void) } =20 shadow_cea_begin =3D kasan_mem_to_shadow_align_down(CPU_ENTRY_AREA_BASE); + shadow_cea_per_cpu_begin =3D kasan_mem_to_shadow_align_up(CPU_ENTRY_AREA_= PER_CPU); shadow_cea_end =3D kasan_mem_to_shadow_align_up(CPU_ENTRY_AREA_BASE + CPU_ENTRY_AREA_MAP_SIZE); =20 @@ -409,6 +410,15 @@ void __init kasan_init(void) kasan_mem_to_shadow((void *)VMALLOC_END + 1), (void *)shadow_cea_begin); =20 + /* + * Populate the shadow for the shared portion of the CPU entry area. + * Shadows for the per-CPU areas are mapped on-demand, as each CPU's + * area is randomly placed somewhere in the 512GiB range and mapping + * the entire 512GiB range is prohibitively expensive. + */ + kasan_populate_shadow(shadow_cea_begin, + shadow_cea_per_cpu_begin, 0); + kasan_populate_early_shadow((void *)shadow_cea_end, kasan_mem_to_shadow((void *)__START_KERNEL_map)); =20 --=20 2.38.1.431.g37b22c650d-goog