From patchwork Fri Aug 26 00:04:33 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kuniyuki Iwashima X-Patchwork-Id: 12955384 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 A2F53ECAAD1 for ; Fri, 26 Aug 2022 00:06:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244166AbiHZAGN (ORCPT ); Thu, 25 Aug 2022 20:06:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33660 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243988AbiHZAGK (ORCPT ); Thu, 25 Aug 2022 20:06:10 -0400 Received: from smtp-fw-9102.amazon.com (smtp-fw-9102.amazon.com [207.171.184.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 281BEC7426; Thu, 25 Aug 2022 17:06:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1661472369; x=1693008369; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=EVJmwtFmjoSMCLp5woTEC52zQFeunS69QTL7PANK91k=; b=uUru8t3YmD7nUKrfQHY67YhNuJl6+LZYmtS6YgpG9CE9K0yvMPywh/B4 +HFRGY5v1/UaIxP3zG1fUozlEitKqSQfCcOnqQ+4NqKfn3AX0ejasJKPK UnJAij3aXOLb9E0SQsTOybneGlp69lQWgi4UiH5eecGzz0u8+dsGGqviT g=; X-IronPort-AV: E=Sophos;i="5.93,264,1654560000"; d="scan'208";a="253012151" Received: from pdx4-co-svc-p1-lb2-vlan2.amazon.com (HELO email-inbound-relay-pdx-2b-1f9d5b26.us-west-2.amazon.com) ([10.25.36.210]) by smtp-border-fw-9102.sea19.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Aug 2022 00:05:54 +0000 Received: from EX13MTAUWB001.ant.amazon.com (pdx1-ws-svc-p6-lb9-vlan3.pdx.amazon.com [10.236.137.198]) by email-inbound-relay-pdx-2b-1f9d5b26.us-west-2.amazon.com (Postfix) with ESMTPS id 8690244C8C; Fri, 26 Aug 2022 00:05:52 +0000 (UTC) Received: from EX19D004ANA001.ant.amazon.com (10.37.240.138) by EX13MTAUWB001.ant.amazon.com (10.43.161.207) with Microsoft SMTP Server (TLS) id 15.0.1497.38; Fri, 26 Aug 2022 00:05:51 +0000 Received: from 88665a182662.ant.amazon.com (10.43.162.140) by EX19D004ANA001.ant.amazon.com (10.37.240.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1118.12; Fri, 26 Aug 2022 00:05:48 +0000 From: Kuniyuki Iwashima To: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Jeff Layton , Chuck Lever , Luis Chamberlain , Kees Cook , Iurii Zaikin CC: Kuniyuki Iwashima , Kuniyuki Iwashima , , Subject: [PATCH v1 net-next 01/13] fs/lock: Revive LOCK_MAND. Date: Thu, 25 Aug 2022 17:04:33 -0700 Message-ID: <20220826000445.46552-2-kuniyu@amazon.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220826000445.46552-1-kuniyu@amazon.com> References: <20220826000445.46552-1-kuniyu@amazon.com> MIME-Version: 1.0 X-Originating-IP: [10.43.162.140] X-ClientProxiedBy: EX13D10UWB001.ant.amazon.com (10.43.161.111) To EX19D004ANA001.ant.amazon.com (10.37.240.138) Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org The commit 90f7d7a0d0d6 ("locks: remove LOCK_MAND flock lock support") removed LOCK_MAND support from the kernel because nothing checked the flag, nor was there no use case. This patch revives LOCK_MAND to introduce a mandatory lock for read/write on /proc/sys. Currently, it's the only use case, so we added two changes while reverting the commit. First, we used to allow any f_mode for LOCK_MAND, but now we don't get it back. Instead, we enforce being FMODE_READ|FMODE_WRITE as LOCK_SH and LOCK_EX. Second, when f_ops->flock() was called with LOCK_MAND, each function returned -EOPNOTSUPP. The following patch does not use f_ops->flock(), so we put the validation before calling f_ops->flock(). Signed-off-by: Kuniyuki Iwashima --- fs/locks.c | 57 ++++++++++++++++++++------------ include/uapi/asm-generic/fcntl.h | 5 --- 2 files changed, 35 insertions(+), 27 deletions(-) diff --git a/fs/locks.c b/fs/locks.c index c266cfdc3291..03ff10a3165e 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -421,6 +421,10 @@ static inline int flock_translate_cmd(int cmd) { case LOCK_UN: return F_UNLCK; } + + if (cmd & LOCK_MAND) + return cmd & (LOCK_MAND | LOCK_RW); + return -EINVAL; } @@ -879,6 +883,10 @@ static bool flock_locks_conflict(struct file_lock *caller_fl, if (caller_fl->fl_file == sys_fl->fl_file) return false; + if (caller_fl->fl_type & LOCK_MAND || + sys_fl->fl_type & LOCK_MAND) + return true; + return locks_conflict(caller_fl, sys_fl); } @@ -2077,9 +2085,7 @@ EXPORT_SYMBOL(locks_lock_inode_wait); * - %LOCK_SH -- a shared lock. * - %LOCK_EX -- an exclusive lock. * - %LOCK_UN -- remove an existing lock. - * - %LOCK_MAND -- a 'mandatory' flock. (DEPRECATED) - * - * %LOCK_MAND support has been removed from the kernel. + * - %LOCK_MAND -- a 'mandatory' flock. (only supported on /proc/sys/) */ SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd) { @@ -2087,19 +2093,6 @@ SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd) struct file_lock fl; struct fd f; - /* - * LOCK_MAND locks were broken for a long time in that they never - * conflicted with one another and didn't prevent any sort of open, - * read or write activity. - * - * Just ignore these requests now, to preserve legacy behavior, but - * throw a warning to let people know that they don't actually work. - */ - if (cmd & LOCK_MAND) { - pr_warn_once("Attempt to set a LOCK_MAND lock via flock(2). This support has been removed and the request ignored.\n"); - return 0; - } - type = flock_translate_cmd(cmd & ~LOCK_NB); if (type < 0) return type; @@ -2109,6 +2102,7 @@ SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd) if (!f.file) return error; + /* LOCK_MAND supports only read/write on proc_sysctl for now */ if (type != F_UNLCK && !(f.file->f_mode & (FMODE_READ | FMODE_WRITE))) goto out_putf; @@ -2122,12 +2116,18 @@ SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd) if (can_sleep) fl.fl_flags |= FL_SLEEP; - if (f.file->f_op->flock) + if (f.file->f_op->flock) { + if (cmd & LOCK_MAND) { + error = -EOPNOTSUPP; + goto out_putf; + } + error = f.file->f_op->flock(f.file, (can_sleep) ? F_SETLKW : F_SETLK, &fl); - else + } else { error = locks_lock_file_wait(f.file, &fl); + } out_putf: fdput(f); @@ -2711,7 +2711,11 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl, seq_printf(f, " %s ", (inode == NULL) ? "*NOINODE*" : "ADVISORY "); } else if (IS_FLOCK(fl)) { - seq_puts(f, "FLOCK ADVISORY "); + if (fl->fl_type & LOCK_MAND) { + seq_puts(f, "FLOCK MANDATORY "); + } else { + seq_puts(f, "FLOCK ADVISORY "); + } } else if (IS_LEASE(fl)) { if (fl->fl_flags & FL_DELEG) seq_puts(f, "DELEG "); @@ -2727,10 +2731,19 @@ static void lock_get_status(struct seq_file *f, struct file_lock *fl, } else { seq_puts(f, "UNKNOWN UNKNOWN "); } - type = IS_LEASE(fl) ? target_leasetype(fl) : fl->fl_type; - seq_printf(f, "%s ", (type == F_WRLCK) ? "WRITE" : - (type == F_RDLCK) ? "READ" : "UNLCK"); + if (fl->fl_type & LOCK_MAND) { + seq_printf(f, "%s ", + (fl->fl_type & LOCK_READ) + ? (fl->fl_type & LOCK_WRITE) ? "RW " : "READ " + : (fl->fl_type & LOCK_WRITE) ? "WRITE" : "NONE "); + } else { + type = IS_LEASE(fl) ? target_leasetype(fl) : fl->fl_type; + + seq_printf(f, "%s ", (type == F_WRLCK) ? "WRITE" : + (type == F_RDLCK) ? "READ" : "UNLCK"); + } + if (inode) { /* userspace relies on this representation of dev_t */ seq_printf(f, "%d %02x:%02x:%lu ", fl_pid, diff --git a/include/uapi/asm-generic/fcntl.h b/include/uapi/asm-generic/fcntl.h index 1ecdb911add8..94fb8c6fd543 100644 --- a/include/uapi/asm-generic/fcntl.h +++ b/include/uapi/asm-generic/fcntl.h @@ -180,11 +180,6 @@ struct f_owner_ex { #define LOCK_NB 4 /* or'd with one of the above to prevent blocking */ #define LOCK_UN 8 /* remove lock */ - -/* - * LOCK_MAND support has been removed from the kernel. We leave the symbols - * here to not break legacy builds, but these should not be used in new code. - */ #define LOCK_MAND 32 /* This is a mandatory flock ... */ #define LOCK_READ 64 /* which allows concurrent read operations */ #define LOCK_WRITE 128 /* which allows concurrent write operations */