From patchwork Mon Oct 30 06:37:09 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jinjie Ruan X-Patchwork-Id: 13440075 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 10A15C4167B for ; Mon, 30 Oct 2023 06:38:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-ID:Date:Subject:CC :To:From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Owner; bh=YHZyIWrjsvcY487VADGZp/ELadgZTqxvoTn2XozG1ZI=; b=uN159QUQTXrWOn YG8Ycapl7FOPiDSH5YbMwplzhw6qlU244tPqtG4xqysMlyURojUwJw2hZtKy7tIhFkeuhSlcTTB2G 17SHR6Wx+GFUGzVb9md5lldwDqqGefsfwR6RzpwMaapURTrJYGWx5MDQSY5qjSP6mAETeJ5+qcBp9 aN5JnJHKTQaL+hYLoUXnhvxsVPFjP4w0lwjvc/pE5j+jyDGwEq2N5S6GcxV6tu+mN4bhU28Q7H8KX EUeCloZhkQvYUAxdZgcomWzzEK2XDAgqXHx1QZ3x+fcRFyZwnMbnNNOdNZg1M47Gak3VW8mcQY49b dva09vd3UQmgbRyxne8g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qxLue-002gEP-2k; Mon, 30 Oct 2023 06:38:12 +0000 Received: from szxga01-in.huawei.com ([45.249.212.187]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qxLub-002gCr-39 for linux-arm-kernel@lists.infradead.org; Mon, 30 Oct 2023 06:38:12 +0000 Received: from kwepemi500008.china.huawei.com (unknown [172.30.72.54]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4SJk3X2WFqzvQJ0; Mon, 30 Oct 2023 14:32:56 +0800 (CST) Received: from huawei.com (10.67.174.55) by kwepemi500008.china.huawei.com (7.221.188.139) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.31; Mon, 30 Oct 2023 14:37:53 +0800 From: Jinjie Ruan To: , , , , , CC: Subject: [PATCH v4.19] arm64: fix a concurrency issue in emulation_proc_handler() Date: Mon, 30 Oct 2023 06:37:09 +0000 Message-ID: <20231030063709.2443546-1-ruanjinjie@huawei.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-Originating-IP: [10.67.174.55] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To kwepemi500008.china.huawei.com (7.221.188.139) X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231029_233810_383460_D7EC14C8 X-CRM114-Status: GOOD ( 15.02 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org In linux-6.1, the related code is refactored in commit 124c49b1b5d9 ("arm64: armv8_deprecated: rework deprected instruction handling") and this issue was incidentally fixed. I have adapted the patch set to linux stable 5.10. However, 4.19 and 5.10 are too different and the patch set is hard to adapt to 4.19. This patch is to solve the problem of repeated addition of linked lists described below with few changes. How to reproduce: CONFIG_ARMV8_DEPRECATED=y, CONFIG_SWP_EMULATION=y, and CONFIG_DEBUG_LIST=y, then launch two shell executions: #!/bin/bash while [ 1 ]; do echo 1 > /proc/sys/abi/swp done or "echo 1 > /proc/sys/abi/swp" and then aunch two shell executions: #!/bin/bash while [ 1 ]; do echo 0 > /proc/sys/abi/swp done In emulation_proc_handler(), read and write operations are performed on insn->current_mode. In the concurrency scenario, mutex only protects writing insn->current_mode, and not protects the read. Suppose there are two concurrent tasks, task1 updates insn->current_mode to INSN_EMULATE in the critical section, the prev_mode of task2 is still the old data INSN_UNDEF of insn->current_mode. As a result, two tasks call update_insn_emulation_mode twice with prev_mode = INSN_UNDEF and current_mode = INSN_EMULATE, then call register_emulation_hooks twice, resulting in a list_add double problem. After applying this patch, the following list add or list del double warnings never occur. Call trace: __list_add_valid+0xd8/0xe4 register_undef_hook+0x94/0x13c update_insn_emulation_mode+0xd0/0x12c emulation_proc_handler+0xd8/0xf4 proc_sys_call_handler+0x140/0x250 proc_sys_write+0x1c/0x2c new_sync_write+0xec/0x18c vfs_write+0x214/0x2ac ksys_write+0x70/0xfc __arm64_sys_write+0x24/0x30 el0_svc_common.constprop.0+0x7c/0x1bc do_el0_svc+0x2c/0x94 el0_svc+0x20/0x30 el0_sync_handler+0xb0/0xb4 el0_sync+0x160/0x180 Call trace: __list_del_entry_valid+0xac/0x110 unregister_undef_hook+0x34/0x80 update_insn_emulation_mode+0xf0/0x180 emulation_proc_handler+0x8c/0xd8 proc_sys_call_handler+0x1d8/0x208 proc_sys_write+0x14/0x20 new_sync_write+0xf0/0x190 vfs_write+0x304/0x388 ksys_write+0x6c/0x100 __arm64_sys_write+0x1c/0x28 el0_svc_common.constprop.4+0x68/0x188 do_el0_svc+0x24/0xa0 el0_svc+0x14/0x20 el0_sync_handler+0x90/0xb8 el0_sync+0x160/0x180 Fixes: af483947d472 ("arm64: fix oops in concurrently setting insn_emulation sysctls") Cc: stable@vger.kernel.org#4.19.x Cc: gregkh@linuxfoundation.org Signed-off-by: Jinjie Ruan Acked-by: Mark Rutland --- arch/arm64/kernel/armv8_deprecated.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c index 7c69a203cdf8..b8d481c3e26d 100644 --- a/arch/arm64/kernel/armv8_deprecated.c +++ b/arch/arm64/kernel/armv8_deprecated.c @@ -211,10 +211,12 @@ static int emulation_proc_handler(struct ctl_table *table, int write, loff_t *ppos) { int ret = 0; - struct insn_emulation *insn = container_of(table->data, struct insn_emulation, current_mode); - enum insn_emulation_mode prev_mode = insn->current_mode; + struct insn_emulation *insn; + enum insn_emulation_mode prev_mode; mutex_lock(&insn_emulation_mutex); + insn = container_of(table->data, struct insn_emulation, current_mode); + prev_mode = insn->current_mode; ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); if (ret || !write || prev_mode == insn->current_mode)