From nobody Wed Dec 17 09:13:17 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 509B3C32792 for ; Tue, 23 Aug 2022 10:37:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1355747AbiHWKhA (ORCPT ); Tue, 23 Aug 2022 06:37:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44832 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1354774AbiHWKWL (ORCPT ); Tue, 23 Aug 2022 06:22:11 -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 E3346BC1E; Tue, 23 Aug 2022 02:03:32 -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 2530C61499; Tue, 23 Aug 2022 09:03:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2B690C433D6; Tue, 23 Aug 2022 09:03:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1661245411; bh=PcYROYEH61UkQAPOT/SlqQLXKep9xpR3tyBm9FxnUmA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fG/L3atYgcWIW1sSk8Wetxshgri+t0mNIbI96Rv0BCRvH5gE1zuXf/quCtJM4VzRK r51dWUXIdZYJQaGh6ZeVw8sAbK8kbnuzcp3B7Ut8cTqs4VwhGxeWUci6azETH+Dp3k GhODY7oxSffQe5i4xa1VDs1at/18/qvfS4Lej/OM= 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 4.19 040/287] arm64: fix oops in concurrently setting insn_emulation sysctls Date: Tue, 23 Aug 2022 10:23:29 +0200 Message-Id: <20220823080101.614892352@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220823080100.268827165@linuxfoundation.org> References: <20220823080100.268827165@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 181c29af5617..7c69a203cdf8 100644 --- a/arch/arm64/kernel/armv8_deprecated.c +++ b/arch/arm64/kernel/armv8_deprecated.c @@ -62,6 +62,7 @@ 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) { @@ -210,10 +211,10 @@ 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) @@ -226,7 +227,7 @@ 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 @@ -250,7 +251,7 @@ static void __init register_insn_emulation_sysctl(void) 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