From patchwork Tue Jan 14 17:19:10 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Dmitry Safonov X-Patchwork-Id: 11332713 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 6FA66139A for ; Tue, 14 Jan 2020 17:19:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4469C24656 for ; Tue, 14 Jan 2020 17:19:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=arista.com header.i=@arista.com header.b="o7zZznzh" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728761AbgANRT2 (ORCPT ); Tue, 14 Jan 2020 12:19:28 -0500 Received: from mail-pg1-f196.google.com ([209.85.215.196]:33798 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728699AbgANRT1 (ORCPT ); Tue, 14 Jan 2020 12:19:27 -0500 Received: by mail-pg1-f196.google.com with SMTP id r11so6702798pgf.1 for ; Tue, 14 Jan 2020 09:19:27 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=arista.com; s=googlenew; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=sV0m/dXPWRmuP2RjACCvkkMA97TOhcVtBgTEpOrLJfk=; b=o7zZznzhqZFGgU9x2MbhAKw04qYYxhD8b7BKYI/OMvzOHR2NDcQykBrM770RXdPCxU m6UbMbRulyr1pTxNJ+7Ug+Qty0Hrl07WK8bS+OoMtjmhQ0N9scmO0Z7bzoH9D/d2rEIK NmAwp46D4yPecyvTMpDWNVO9MZbDturBdBnOI5ql5FHTB5sQ7rgBBojpdc7/BWZxYgIW m5c3vp8pX5c8lUj8+pKbVBj/BZy3dUj89ALRKwMDK0/lnVdyKokBmHVvWNdmV0jothLt a0UPrZlFaT8RHluzZEFtVM9V2nbcLnHlSJ0i9y5qj2igz2RnnFIOYLPJZOwzLQUYQ2TV OKiA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=sV0m/dXPWRmuP2RjACCvkkMA97TOhcVtBgTEpOrLJfk=; b=KnnfHjszDzCPHNT3IOfhfpcb2WynRKcnGOSgytSRsZyBrOvRXw9wQxrgioOqVK11T0 OUzzWLpD27cLig4MTeV7X5FKDAeynsBqrq2+XMJ/DP+Ts6rnCCECXwEkxRvCKgpIX02/ e+6rzv9L95U4jaO5569Ut1Fr1LK6ilUqPwSdzftcsLTJaIGkjeRrYDgMo4zzWCXJY+x9 uDICaivA1Xq6lfscvQNGeBqI7W7iVtkQrCypjl8WLwsWzjA4rsJT4y3da+66t7111mzO XlEs0LOXR5P+gyZPBEn/5x6mBrwfH9qREuUo43v1WGHOcTwytbChHqjlLWKa+4aHo2P5 ncxQ== X-Gm-Message-State: APjAAAUnae3J207OLUa5DpLecUZkTLKv8LNxE5mJJ7W8Rf+oIzO3Qi7n 2EUAuV1sbNzNUsqpprxVFkVh+A== X-Google-Smtp-Source: APXvYqxnkgB7dODzw4NXcFYzDJCNxG/IKs5tPYtgPo5DN5549y6+1pt2+Cuqa9Ve6PvwtSCgHyCxHQ== X-Received: by 2002:a63:fe50:: with SMTP id x16mr27638703pgj.31.1579022366814; Tue, 14 Jan 2020 09:19:26 -0800 (PST) Received: from Mindolluin.ire.aristanetworks.com ([217.173.96.166]) by smtp.gmail.com with ESMTPSA id m128sm18965687pfm.183.2020.01.14.09.19.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 14 Jan 2020 09:19:26 -0800 (PST) From: Dmitry Safonov To: linux-kernel@vger.kernel.org Cc: Dmitry Safonov <0x7f454c46@gmail.com>, Dmitry Safonov , Greg Kroah-Hartman , Iurii Zaikin , Jiri Slaby , Joe Perches , Randy Dunlap , Vasiliy Khoruzhick , linux-serial@vger.kernel.org, Luis Chamberlain , Kees Cook , linux-fsdevel@vger.kernel.org Subject: [PATCHv2-next 1/3] sysctl/sysrq: Remove __sysrq_enabled copy Date: Tue, 14 Jan 2020 17:19:10 +0000 Message-Id: <20200114171912.261787-2-dima@arista.com> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200114171912.261787-1-dima@arista.com> References: <20200114171912.261787-1-dima@arista.com> MIME-Version: 1.0 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Many embedded boards have a disconnected TTL level serial which can generate some garbage that can lead to spurious false sysrq detects. Currently, sysrq can be either completely disabled for serial console or always disabled (with CONFIG_MAGIC_SYSRQ_SERIAL), since commit 732dbf3a6104 ("serial: do not accept sysrq characters via serial port") At Arista, we have such boards that can generate BREAK and random garbage. While disabling sysrq for serial console would solve the problem with spurious false sysrq triggers, it's also desirable to have a way to enable sysrq back. Having the way to enable sysrq was beneficial to debug lockups with a manual investigation in field and on the other side preventing false sysrq detections. As a preparation to add sysrq_toggle_support() call into uart, remove a private copy of sysrq_enabled from sysctl - it should reflect the actual status of sysrq. Furthermore, the private copy isn't correct already in case sysrq_always_enabled is true. So, remove __sysrq_enabled and use a getter-helper for sysrq enabled status. Cc: Iurii Zaikin Cc: Jiri Slaby Cc: Luis Chamberlain Cc: Kees Cook Cc: linux-fsdevel@vger.kernel.org Signed-off-by: Dmitry Safonov --- drivers/tty/sysrq.c | 7 +++++++ include/linux/sysrq.h | 7 +++++++ kernel/sysctl.c | 41 ++++++++++++++++++++++------------------- 3 files changed, 36 insertions(+), 19 deletions(-) diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c index f724962a5906..ef3e78967146 100644 --- a/drivers/tty/sysrq.c +++ b/drivers/tty/sysrq.c @@ -73,6 +73,13 @@ static bool sysrq_on_mask(int mask) (sysrq_enabled & mask); } +int sysrq_get_mask(void) +{ + if (sysrq_always_enabled) + return 1; + return sysrq_enabled; +} + static int __init sysrq_always_enabled_setup(char *str) { sysrq_always_enabled = true; diff --git a/include/linux/sysrq.h b/include/linux/sysrq.h index 8c71874e8485..ad09a7eefda2 100644 --- a/include/linux/sysrq.h +++ b/include/linux/sysrq.h @@ -50,6 +50,7 @@ int unregister_sysrq_key(int key, struct sysrq_key_op *op); struct sysrq_key_op *__sysrq_get_key_op(int key); int sysrq_toggle_support(int enable_mask); +int sysrq_get_mask(void); #else @@ -71,6 +72,12 @@ static inline int unregister_sysrq_key(int key, struct sysrq_key_op *op) return -EINVAL; } +static inline int sysrq_get_mask(void) +{ + /* Magic SysRq disabled mask */ + return 0; +} + #endif #endif /* _LINUX_SYSRQ_H */ diff --git a/kernel/sysctl.c b/kernel/sysctl.c index d396aaaf19a3..6ddb4d7df0e1 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -229,25 +229,8 @@ static int proc_dopipe_max_size(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos); #ifdef CONFIG_MAGIC_SYSRQ -/* Note: sysrq code uses its own private copy */ -static int __sysrq_enabled = CONFIG_MAGIC_SYSRQ_DEFAULT_ENABLE; - static int sysrq_sysctl_handler(struct ctl_table *table, int write, - void __user *buffer, size_t *lenp, - loff_t *ppos) -{ - int error; - - error = proc_dointvec(table, write, buffer, lenp, ppos); - if (error) - return error; - - if (write) - sysrq_toggle_support(__sysrq_enabled); - - return 0; -} - + void __user *buffer, size_t *lenp, loff_t *ppos); #endif static struct ctl_table kern_table[]; @@ -747,7 +730,7 @@ static struct ctl_table kern_table[] = { #ifdef CONFIG_MAGIC_SYSRQ { .procname = "sysrq", - .data = &__sysrq_enabled, + .data = NULL, .maxlen = sizeof (int), .mode = 0644, .proc_handler = sysrq_sysctl_handler, @@ -2844,6 +2827,26 @@ static int proc_dostring_coredump(struct ctl_table *table, int write, } #endif +#ifdef CONFIG_MAGIC_SYSRQ +static int sysrq_sysctl_handler(struct ctl_table *table, int write, + void __user *buffer, size_t *lenp, loff_t *ppos) +{ + int tmp, ret; + + tmp = sysrq_get_mask(); + + ret = __do_proc_dointvec(&tmp, table, write, buffer, + lenp, ppos, NULL, NULL); + if (ret || !write) + return ret; + + if (write) + sysrq_toggle_support(tmp); + + return 0; +} +#endif + static int __do_proc_doulongvec_minmax(void *data, struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos,