From nobody Fri Dec 19 20:52:45 2025 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 B286DC32772 for ; Tue, 23 Aug 2022 09:38:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351699AbiHWJix (ORCPT ); Tue, 23 Aug 2022 05:38:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52568 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1351575AbiHWJh6 (ORCPT ); Tue, 23 Aug 2022 05:37:58 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EE93232B89; Tue, 23 Aug 2022 01:40:39 -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 1577361517; Tue, 23 Aug 2022 08:39:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1F263C433D7; Tue, 23 Aug 2022 08:39:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1661243989; bh=5F9RsjFgVNOGiSc2oDB5+Far0a7iC5ApU7VDGncrxM0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=LfziJT/DabePtSgAyMxlobBpsGxqozCktToWfc8I1nHbSpeDg+kj2KWcMJUR/ziYE 0b2xgZKBoKKfMKTB73SAuo0sfXRlVCKyVnZmn59Q+kBxTHtVD1rjMf3NDC0yM8Z3Je H1VlFMWKFM01R+PeP4xM7VkwhFQ4AxO4aI7podFQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, hewenliang , Haibin Zhang , Catalin Marinas , Will Deacon , Sasha Levin Subject: [PATCH 4.14 040/229] arm64: fix oops in concurrently setting insn_emulation sysctls Date: Tue, 23 Aug 2022 10:23:21 +0200 Message-Id: <20220823080055.024139667@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220823080053.202747790@linuxfoundation.org> References: <20220823080053.202747790@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: haibinzhang (=E5=BC=A0=E6=B5=B7=E6=96=8C) [ Upstream commit af483947d472eccb79e42059276c4deed76f99a6 ] emulation_proc_handler() changes table->data for proc_dointvec_minmax and can generate the following Oops if called concurrently with itself: | Unable to handle kernel NULL pointer dereference at virtual address 0000= 000000000010 | Internal error: Oops: 96000006 [#1] SMP | Call trace: | update_insn_emulation_mode+0xc0/0x148 | emulation_proc_handler+0x64/0xb8 | proc_sys_call_handler+0x9c/0xf8 | proc_sys_write+0x18/0x20 | __vfs_write+0x20/0x48 | vfs_write+0xe4/0x1d0 | ksys_write+0x70/0xf8 | __arm64_sys_write+0x20/0x28 | el0_svc_common.constprop.0+0x7c/0x1c0 | el0_svc_handler+0x2c/0xa0 | el0_svc+0x8/0x200 To fix this issue, keep the table->data as &insn->current_mode and use container_of() to retrieve the insn pointer. Another mutex is used to protect against the current_mode update but not for retrieving insn_emulation as table->data is no longer changing. Co-developed-by: hewenliang Signed-off-by: hewenliang Signed-off-by: Haibin Zhang Reviewed-by: Catalin Marinas Link: https://lore.kernel.org/r/20220128090324.2727688-1-hewenliang4@huawei= .com Link: https://lore.kernel.org/r/9A004C03-250B-46C5-BF39-782D7551B00E@tencen= t.com Signed-off-by: Will Deacon Signed-off-by: Sasha Levin --- arch/arm64/kernel/armv8_deprecated.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8= _deprecated.c index 092046704cbc..b82e32daaf66 100644 --- a/arch/arm64/kernel/armv8_deprecated.c +++ b/arch/arm64/kernel/armv8_deprecated.c @@ -63,6 +63,7 @@ struct insn_emulation { static LIST_HEAD(insn_emulation); static int nr_insn_emulated __initdata; static DEFINE_RAW_SPINLOCK(insn_emulation_lock); +static DEFINE_MUTEX(insn_emulation_mutex); =20 static void register_emulation_hooks(struct insn_emulation_ops *ops) { @@ -208,10 +209,10 @@ static int emulation_proc_handler(struct ctl_table *t= able, int write, loff_t *ppos) { int ret =3D 0; - struct insn_emulation *insn =3D (struct insn_emulation *) table->data; + struct insn_emulation *insn =3D container_of(table->data, struct insn_emu= lation, current_mode); enum insn_emulation_mode prev_mode =3D insn->current_mode; =20 - table->data =3D &insn->current_mode; + mutex_lock(&insn_emulation_mutex); ret =3D proc_dointvec_minmax(table, write, buffer, lenp, ppos); =20 if (ret || !write || prev_mode =3D=3D insn->current_mode) @@ -224,7 +225,7 @@ static int emulation_proc_handler(struct ctl_table *tab= le, int write, update_insn_emulation_mode(insn, INSN_UNDEF); } ret: - table->data =3D insn; + mutex_unlock(&insn_emulation_mutex); return ret; } =20 @@ -254,7 +255,7 @@ static void __init register_insn_emulation_sysctl(struc= t ctl_table *table) sysctl->maxlen =3D sizeof(int); =20 sysctl->procname =3D insn->ops->name; - sysctl->data =3D insn; + sysctl->data =3D &insn->current_mode; sysctl->extra1 =3D &insn->min; sysctl->extra2 =3D &insn->max; sysctl->proc_handler =3D emulation_proc_handler; --=20 2.35.1