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 X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id F1DF3C433E0 for ; Thu, 25 Feb 2021 20:27:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BB22064F1B for ; Thu, 25 Feb 2021 20:27:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233942AbhBYU0q (ORCPT ); Thu, 25 Feb 2021 15:26:46 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:38254 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232906AbhBYUZ0 (ORCPT ); Thu, 25 Feb 2021 15:25:26 -0500 From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1614284683; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=GUh9AQdpak/Ivn7suhyTdO/F4X3qfKOJJGmaxcJ3ou4=; b=3rHpCJLHGUEZEUa+05r79KAjvENed3E6xoEkW4h/Ov9ZdgAUedH7h7aEn4ooBmSJPyu9NQ CrR2WrwdcD5kJUUYNVbkBjnIWWWiDqutH9s+chL450OtkIDcEgpsEWhsSmZE13bB9WFCAY FCsc4o0Mj9Scpp8IT8M5vqgRaEnogD87VE0i3Jki6dMpnZ1r8Rf2k9TaLQBnq3ZlnB4gcy mhyeODnchqIq2EsHjc8zdH9glr4lhM7DUXwWY7ixqtIkY4OGNe479WTFYpaMyTCA4ohtXG czQ/Iy3bzVKqzf8Nxh5SDXlNO/TcQKS3KQIQnz4ITZhszXjiw2ZtFV1GSXuXhw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1614284683; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=GUh9AQdpak/Ivn7suhyTdO/F4X3qfKOJJGmaxcJ3ou4=; b=mwAUBtTK54L6//Yc2C+BYtk6+GycE0XYesQ2ntnXLjyRNy9FwJe1RJlglOKHXqHxbD8Q+G zLHGxEIp5i/eQxCw== To: Petr Mladek Cc: Sergey Senozhatsky , Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: [PATCH next v3 09/15] printk: use atomic64_t for devkmsg_user.seq Date: Thu, 25 Feb 2021 21:24:32 +0100 Message-Id: <20210225202438.28985-10-john.ogness@linutronix.de> In-Reply-To: <20210225202438.28985-1-john.ogness@linutronix.de> References: <20210225202438.28985-1-john.ogness@linutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org @user->seq is indirectly protected by @logbuf_lock. Once @logbuf_lock is removed, @user->seq will be no longer safe from an atomicity point of view. In preparation for the removal of @logbuf_lock, change it to atomic64_t to provide this safety. Signed-off-by: John Ogness Reviewed-by: Petr Mladek --- kernel/printk/printk.c | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index b78b85947312..82d89eec4aac 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -662,7 +662,7 @@ static ssize_t msg_print_ext_body(char *buf, size_t size, /* /dev/kmsg - userspace message inject/listen interface */ struct devkmsg_user { - u64 seq; + atomic64_t seq; struct ratelimit_state rs; struct mutex lock; char buf[CONSOLE_EXT_LOG_MAX]; @@ -763,7 +763,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf, return ret; logbuf_lock_irq(); - if (!prb_read_valid(prb, user->seq, r)) { + if (!prb_read_valid(prb, atomic64_read(&user->seq), r)) { if (file->f_flags & O_NONBLOCK) { ret = -EAGAIN; logbuf_unlock_irq(); @@ -772,15 +772,15 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf, logbuf_unlock_irq(); ret = wait_event_interruptible(log_wait, - prb_read_valid(prb, user->seq, r)); + prb_read_valid(prb, atomic64_read(&user->seq), r)); if (ret) goto out; logbuf_lock_irq(); } - if (r->info->seq != user->seq) { + if (r->info->seq != atomic64_read(&user->seq)) { /* our last seen message is gone, return error and reset */ - user->seq = r->info->seq; + atomic64_set(&user->seq, r->info->seq); ret = -EPIPE; logbuf_unlock_irq(); goto out; @@ -791,7 +791,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf, &r->text_buf[0], r->info->text_len, &r->info->dev_info); - user->seq = r->info->seq + 1; + atomic64_set(&user->seq, r->info->seq + 1); logbuf_unlock_irq(); if (len > count) { @@ -831,7 +831,7 @@ static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence) switch (whence) { case SEEK_SET: /* the first record */ - user->seq = prb_first_valid_seq(prb); + atomic64_set(&user->seq, prb_first_valid_seq(prb)); break; case SEEK_DATA: /* @@ -839,11 +839,11 @@ static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence) * like issued by 'dmesg -c'. Reading /dev/kmsg itself * changes no global state, and does not clear anything. */ - user->seq = latched_seq_read_nolock(&clear_seq); + atomic64_set(&user->seq, latched_seq_read_nolock(&clear_seq)); break; case SEEK_END: /* after the last record */ - user->seq = prb_next_seq(prb); + atomic64_set(&user->seq, prb_next_seq(prb)); break; default: ret = -EINVAL; @@ -864,9 +864,9 @@ static __poll_t devkmsg_poll(struct file *file, poll_table *wait) poll_wait(file, &log_wait, wait); logbuf_lock_irq(); - if (prb_read_valid_info(prb, user->seq, &info, NULL)) { + if (prb_read_valid_info(prb, atomic64_read(&user->seq), &info, NULL)) { /* return error when data has vanished underneath us */ - if (info.seq != user->seq) + if (info.seq != atomic64_read(&user->seq)) ret = EPOLLIN|EPOLLRDNORM|EPOLLERR|EPOLLPRI; else ret = EPOLLIN|EPOLLRDNORM; @@ -905,7 +905,7 @@ static int devkmsg_open(struct inode *inode, struct file *file) &user->text_buf[0], sizeof(user->text_buf)); logbuf_lock_irq(); - user->seq = prb_first_valid_seq(prb); + atomic64_set(&user->seq, prb_first_valid_seq(prb)); logbuf_unlock_irq(); file->private_data = user; -- 2.20.1