From mboxrd@z Thu Jan 1 00:00:00 1970 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 C5B77C4332F for ; Fri, 9 Dec 2022 11:10:48 +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:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=3kufYMXYCA9tyIgtFo73grJQxwVgnOKowLKbjI0b4IM=; b=sW7GE2wVZ8TMKE glHpl6CNSzL92WR4YXERDklEKEHtzIStrNtTEwIFW9lhfj36vOE7aqORv+vm9Xc6UrpnedKnR6tq8 2rUMnQ02yYriQmzPGu51rtAfI5uCJ8SkwMY+5U+scdv4XY4HvfLxruyhcLBC+20oJdZkwq0k0yiZ0 T7asnOBZXRl5i7XIRxxBGOnbUBbn3UrJIzmLpcWgdjyeCmBIwwZtCACtA2TfPawkLpRPRUuPzAbh9 04nbx5UyhNPsZNw3jUwmeHyYpyAMfvru6ksmdSd3AIIkFjd7dNoNQ8411EtIhpK1EE8ASbRyTr9Wr a4DlUcjhN3hhnYl6c49A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1p3bGO-0073L9-4C; Fri, 09 Dec 2022 11:09:56 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1p3bGK-0073K1-Un for linux-arm-kernel@lists.infradead.org; Fri, 09 Dec 2022 11:09:54 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DA46023A; Fri, 9 Dec 2022 03:09:57 -0800 (PST) Received: from FVFF77S0Q05N (unknown [10.57.39.232]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E52CD3F73B; Fri, 9 Dec 2022 03:09:49 -0800 (PST) Date: Fri, 9 Dec 2022 11:09:47 +0000 From: Mark Rutland To: ruanjinjie Cc: catalin.marinas@arm.com, will@kernel.org, haibinzhang@tencent.com, hewenliang4@huawei.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] arm64: fix a concurrency issue in emulation_proc_handler() Message-ID: References: <20221209105556.47621-1-ruanjinjie@huawei.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20221209105556.47621-1-ruanjinjie@huawei.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221209_030953_055330_E17B98B3 X-CRM114-Status: GOOD ( 21.78 ) 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: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Dec 09, 2022 at 06:55:56PM +0800, ruanjinjie wrote: > 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. > > 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 The version queued in the arm64 for-next/core branch no longer has the list manipulation, but we do need to fix this for stable, and there is a remaining race on reading insn->current_mode in emulation_proc_handler(). > Fixes: af483947d472 ("arm64: fix oops in concurrently setting insn_emulation sysctls") > Signed-off-by: ruanjinjie > --- > 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 fb0e7c7b2e20..d33e5d9e6990 100644 > --- a/arch/arm64/kernel/armv8_deprecated.c > +++ b/arch/arm64/kernel/armv8_deprecated.c > @@ -208,10 +208,12 @@ 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); We don't strictly need to move the container_of(), but it makes no odds either way, and this looks good to me: Acked-by: Mark Rutland Mark. > > if (ret || !write || prev_mode == insn->current_mode) > -- > 2.25.1 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel