From nobody Thu May 14 06:45:00 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 E415BC433F5 for ; Fri, 8 Apr 2022 12:01:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234168AbiDHMDV (ORCPT ); Fri, 8 Apr 2022 08:03:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58700 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235416AbiDHMCv (ORCPT ); Fri, 8 Apr 2022 08:02:51 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E14E52EC for ; Fri, 8 Apr 2022 05:00:47 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 7DA2962066 for ; Fri, 8 Apr 2022 12:00:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6DBB7C385A3; Fri, 8 Apr 2022 12:00:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1649419246; bh=DRv3mm8f90dK7Yzygr45t/zBtQo9zFMAVRIqHpVBdwE=; h=Date:From:To:Cc:Subject:From; b=G3w5x4c++6cZhm+qV6V7vd7WWzsoQpPUtw5fKyO0m9gfkdtJC+1jqUjukQxnLZAku JarSUwGfNA2+dPkrgDu/zXY8dwaKdizyLQaO18QdRnHbVlzzHZakaUrgGljVGdD8+h DjG+0T0t4GbM7QKjWIfWp95cLUPpnLWNA/FjRsw3AKqzFuj84ebJCmHJNcLQJA5vc8 21MH8q7oimWZKavhaaFzWB8oDht5nMdNrwW70RCRaW2EuzQCQ6H0o/3H5PgLPpqGcL 8hoB4m7SJ2BrCQJr4f8Mz91Xv4aOkoUlgi7CUH6Yl3e0dtYRYEIhu8zJB5fD74zQTW iir8FTQI594pQ== Date: Fri, 8 Apr 2022 13:00:41 +0100 From: Will Deacon To: linux-arm-kernel@lists.infradead.org, james.morse@arm.com Cc: linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org, maz@kernel.org, catalin.marinas@arm.com, mark.rutland@arm.com Subject: arm64 spectre-bhb backports break boot on stable kernels <= v5.4 Message-ID: <20220408120041.GB27685@willie-the-truck> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Hi James, Booting stable kernels <=3D v5.4 on arm64 with CONFIG_HARDEN_BRANCH_PREDICT= OR=3Dn results in a NULL pointer dereference during boot due to kvm_get_hyp_vector= () dereferencing a NULL pointer from arm64_get_bp_hardening_data(): [ 2.384444] Internal error: Oops: 96000004 [#1] PREEMPT SMP [ 2.384461] pstate: 20400085 (nzCv daIf +PAN -UAO) [ 2.384472] pc : cpu_hyp_reinit+0x114/0x30c [ 2.384476] lr : cpu_hyp_reinit+0x80/0x30c [ 2.384477] sp : ffff800010013e20 [ 2.384479] x29: ffff800010013e20 x28: ffff0000df033f00 [ 2.384484] x27: ffff800011caa000 x26: ffff0000de58e000 [ 2.384487] x25: ffff800011e57000 x24: ffff800011caad90 [ 2.384490] x23: ffff800011c778e0 x22: ffff800011a56000 [ 2.384494] x21: ffff800011a56000 x20: 0000b471121a6000 [ 2.384497] x19: 00000000de588000 x18: 0000000000000000 [ 2.384500] x17: 0000000000000000 x16: 0000000000000400 [ 2.384503] x15: 0000000000001000 x14: 00000000000007f2 [ 2.384507] x13: 0000000000000004 x12: 0000000000000002 [ 2.384510] x11: 0000000000000000 x10: 00000000121a6000 [ 2.384513] x9 : ffff800011c77fd8 x8 : 0000000000000010 [ 2.384516] x7 : 4f422effff306b64 x6 : 0000008080000000 [ 2.384519] x5 : 0000008080000000 x4 : ffff800011fabc94 [ 2.384522] x3 : ffff800011f5bde0 x2 : 0000000000000001 [ 2.384526] x1 : 00000000121a0000 x0 : ffff8000118f962d [ 2.384529] Call trace: [ 2.384533] cpu_hyp_reinit+0x114/0x30c [ 2.384537] _kvm_arch_hardware_enable+0x30/0x54 [ 2.384541] flush_smp_call_function_queue+0xe4/0x154 [ 2.384544] generic_smp_call_function_single_interrupt+0x10/0x18 [ 2.384549] ipi_handler+0x170/0x2b0 [ 2.384555] handle_percpu_devid_fasteoi_ipi+0x120/0x1cc [ 2.384560] __handle_domain_irq+0x9c/0xf4 [ 2.384563] gic_handle_irq+0x6c/0xe4 [ 2.384566] el1_irq+0xf0/0x1c0 [ 2.384570] arch_cpu_idle+0x28/0x44 [ 2.384574] do_idle+0x100/0x2a8 [ 2.384577] cpu_startup_entry+0x20/0x24 [ 2.384581] secondary_start_kernel+0x1b0/0x1cc [ 2.384589] Code: b9469d08 7100011f 540003ad 52800208 (f9400108) [ 2.384600] ---[ end trace 266d08dbf96ff143 ]--- [ 2.385171] Kernel panic - not syncing: Fatal exception in interrupt The faulting load is the access to 'data->template_start', for which the compiler emits the hilarious: mov w8, #0x10 ldr x8, [x8] I can bodge this as below (untested), but it's pretty grotty. Please can you take a look? Cheers, Will --->8 diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c index 33b33416fea4..3bc1380f5524 100644 --- a/arch/arm64/kernel/cpu_errata.c +++ b/arch/arm64/kernel/cpu_errata.c @@ -939,6 +939,7 @@ const struct arm64_cpu_capabilities arm64_errata[] =3D { .cpu_enable =3D cpu_enable_ssbd_mitigation, .midr_range_list =3D arm64_ssb_cpus, }, +#ifdef CONFIG_HARDEN_BRANCH_PREDICTOR { .desc =3D "Spectre-BHB", .capability =3D ARM64_SPECTRE_BHB, @@ -946,6 +947,7 @@ const struct arm64_cpu_capabilities arm64_errata[] =3D { .matches =3D is_spectre_bhb_affected, .cpu_enable =3D spectre_bhb_enable_mitigation, }, +#endif #ifdef CONFIG_ARM64_ERRATUM_1418040 { .desc =3D "ARM erratum 1418040",