From patchwork Wed Aug 1 15:27:28 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 10552545 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 4AF5C157D for ; Wed, 1 Aug 2018 15:28:03 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3A5A22A65C for ; Wed, 1 Aug 2018 15:28:03 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 2EECC2A6D8; Wed, 1 Aug 2018 15:28:03 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id ADED92A65C for ; Wed, 1 Aug 2018 15:28:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389809AbeHARNr (ORCPT ); Wed, 1 Aug 2018 13:13:47 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:58752 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2389770AbeHARNq (ORCPT ); Wed, 1 Aug 2018 13:13:46 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 88DAC7A7E6; Wed, 1 Aug 2018 15:27:31 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-120-116.rdu2.redhat.com [10.10.120.116]) by smtp.corp.redhat.com (Postfix) with ESMTP id 19C21200AC23; Wed, 1 Aug 2018 15:27:30 +0000 (UTC) Organization: Red Hat UK Ltd. 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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 30/33] vfs: syscall: Add fspick() to select a superblock for reconfiguration [ver #11] From: David Howells To: viro@zeniv.linux.org.uk Cc: linux-api@vger.kernel.org, torvalds@linux-foundation.org, dhowells@redhat.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Wed, 01 Aug 2018 16:27:28 +0100 Message-ID: <153313724861.13253.3837522702693613670.stgit@warthog.procyon.org.uk> In-Reply-To: <153313703562.13253.5766498657900728120.stgit@warthog.procyon.org.uk> References: <153313703562.13253.5766498657900728120.stgit@warthog.procyon.org.uk> User-Agent: StGit/unknown-version MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Wed, 01 Aug 2018 15:27:31 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Wed, 01 Aug 2018 15:27:31 +0000 (UTC) for IP:'10.11.54.6' DOMAIN:'int-mx06.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'dhowells@redhat.com' RCPT:'' Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Provide an fspick() system call that can be used to pick an existing mountpoint into an fs_context which can thereafter be used to reconfigure a superblock (equivalent of the superblock side of -o remount). This looks like: int fd = fspick(AT_FDCWD, "/mnt", FSPICK_CLOEXEC | FSPICK_NO_AUTOMOUNT); fsconfig(fd, FSCONFIG_SET_FLAG, "intr", NULL, 0); fsconfig(fd, FSCONFIG_SET_FLAG, "noac", NULL, 0); fsconfig(fd, FSCONFIG_CMD_RECONFIGURE, NULL, NULL, 0); At the point of fspick being called, the file descriptor referring to the filesystem context is in exactly the same state as the one that was created by fsopen() after fsmount() has been successfully called. Signed-off-by: David Howells cc: linux-api@vger.kernel.org --- arch/x86/entry/syscalls/syscall_32.tbl | 1 + arch/x86/entry/syscalls/syscall_64.tbl | 1 + fs/fsopen.c | 58 ++++++++++++++++++++++++++++++++ include/linux/syscalls.h | 1 + include/uapi/linux/fs.h | 5 +++ 5 files changed, 66 insertions(+) diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl index c78b68256f8a..d1eb6c815790 100644 --- a/arch/x86/entry/syscalls/syscall_32.tbl +++ b/arch/x86/entry/syscalls/syscall_32.tbl @@ -403,3 +403,4 @@ 389 i386 fsopen sys_fsopen __ia32_sys_fsopen 390 i386 fsconfig sys_fsconfig __ia32_sys_fsconfig 391 i386 fsmount sys_fsmount __ia32_sys_fsmount +392 i386 fspick sys_fspick __ia32_sys_fspick diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl index d44ead5d4368..d3ab703c02bb 100644 --- a/arch/x86/entry/syscalls/syscall_64.tbl +++ b/arch/x86/entry/syscalls/syscall_64.tbl @@ -348,6 +348,7 @@ 337 common fsopen __x64_sys_fsopen 338 common fsconfig __x64_sys_fsconfig 339 common fsmount __x64_sys_fsmount +340 common fspick __x64_sys_fspick # # x32-specific system call numbers start at 512 to avoid cache impact diff --git a/fs/fsopen.c b/fs/fsopen.c index 5d8560e78ce1..e79bb5b085d6 100644 --- a/fs/fsopen.c +++ b/fs/fsopen.c @@ -155,6 +155,64 @@ SYSCALL_DEFINE2(fsopen, const char __user *, _fs_name, unsigned int, flags) return ret; } +/* + * Pick a superblock into a context for reconfiguration. + */ +SYSCALL_DEFINE3(fspick, int, dfd, const char __user *, path, unsigned int, flags) +{ + struct fs_context *fc; + struct path target; + unsigned int lookup_flags; + int ret; + + if (!ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN)) + return -EPERM; + + if ((flags & ~(FSPICK_CLOEXEC | + FSPICK_SYMLINK_NOFOLLOW | + FSPICK_NO_AUTOMOUNT | + FSPICK_EMPTY_PATH)) != 0) + return -EINVAL; + + lookup_flags = LOOKUP_FOLLOW | LOOKUP_AUTOMOUNT; + if (flags & FSPICK_SYMLINK_NOFOLLOW) + lookup_flags &= ~LOOKUP_FOLLOW; + if (flags & FSPICK_NO_AUTOMOUNT) + lookup_flags &= ~LOOKUP_AUTOMOUNT; + if (flags & FSPICK_EMPTY_PATH) + lookup_flags |= LOOKUP_EMPTY; + ret = user_path_at(dfd, path, lookup_flags, &target); + if (ret < 0) + goto err; + + ret = -EOPNOTSUPP; + if (!target.dentry->d_sb->s_op->reconfigure) + goto err_path; + + fc = vfs_new_fs_context(target.dentry->d_sb->s_type, target.dentry, + 0, FS_CONTEXT_FOR_RECONFIGURE); + if (IS_ERR(fc)) { + ret = PTR_ERR(fc); + goto err_path; + } + + fc->phase = FS_CONTEXT_RECONF_PARAMS; + + ret = fscontext_alloc_log(fc); + if (ret < 0) + goto err_fc; + + path_put(&target); + return fscontext_create_fd(fc, flags & FSPICK_CLOEXEC ? O_CLOEXEC : 0); + +err_fc: + put_fs_context(fc); +err_path: + path_put(&target); +err: + return ret; +} + /* * Check the state and apply the configuration. Note that this function is * allowed to 'steal' the value by setting param->xxx to NULL before returning. diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 65db661cc2da..701522957a12 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -908,6 +908,7 @@ asmlinkage long sys_fsopen(const char __user *fs_name, unsigned int flags); asmlinkage long sys_fsconfig(int fs_fd, unsigned int cmd, const char __user *key, const void __user *value, int aux); asmlinkage long sys_fsmount(int fs_fd, unsigned int flags, unsigned int ms_flags); +asmlinkage long sys_fspick(int dfd, const char __user *path, unsigned int flags); /* * Architecture-specific system calls diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index 10281d582e28..7f01503a9e9b 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -351,6 +351,11 @@ typedef int __bitwise __kernel_rwf_t; #define FSMOUNT_CLOEXEC 0x00000001 +#define FSPICK_CLOEXEC 0x00000001 +#define FSPICK_SYMLINK_NOFOLLOW 0x00000002 +#define FSPICK_NO_AUTOMOUNT 0x00000004 +#define FSPICK_EMPTY_PATH 0x00000008 + /* * The type of fsconfig() call made. */