[02/33] vfs: syscall: Add move_mount(2) to move mounts around [ver #11]

Message ID	153313705821.13253.15519769348603350410.stgit@warthog.procyon.org.uk (mailing list archive)
State	New, archived
Headers	show Return-Path: <linux-fsdevel-owner@kernel.org> Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 02/33] vfs: syscall: Add move_mount(2) to move mounts around [ver #11] From: David Howells <dhowells@redhat.com> 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 16:24:18 +0100 Message-ID: <153313705821.13253.15519769348603350410.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 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk
Series	VFS: Introduce filesystem context [ver #11] \| expand [00/33] VFS: Introduce filesystem context [ver #11] [01/33] vfs: syscall: Add open_tree(2) to reference or clone a mount [ver #11] [02/33] vfs: syscall: Add move_mount(2) to move mounts around [ver #11] [03/33] teach move_mount(2) to work with OPEN_TREE_CLONE [ver #11] [04/33] vfs: Suppress MS_* flag defs within the kernel unless explicitly enabled [ver #11] [05/33] vfs: Introduce the basic header for the new mount API's filesystem context [ver #11] [06/33] vfs: Introduce logging functions [ver #11] [07/33] vfs: Add configuration parser helpers [ver #11] [08/33] vfs: Add LSM hooks for the new mount API [ver #11] [09/33] selinux: Implement the new mount API LSM hooks [ver #11] [10/33] smack: Implement filesystem context security hooks [ver #11] [11/33] apparmor: Implement security hooks for the new mount API [ver #11] [12/33] tomoyo: Implement security hooks for the new mount API [ver #11] [13/33] vfs: Separate changing mount flags full remount [ver #11] [14/33] vfs: Implement a filesystem superblock creation/configuration context [ver #11] [15/33] vfs: Remove unused code after filesystem context changes [ver #11] [16/33] procfs: Move proc_fill_super() to fs/proc/root.c [ver #11] [17/33] proc: Add fs_context support to procfs [ver #11] [18/33] ipc: Convert mqueue fs to fs_context [ver #11] [19/33] cpuset: Use fs_context [ver #11] [20/33] kernfs, sysfs, cgroup, intel_rdt: Support fs_context [ver #11] [21/33] hugetlbfs: Convert to fs_context [ver #11] [22/33] vfs: Remove kern_mount_data() [ver #11] [23/33] vfs: Provide documentation for new mount API [ver #11] [24/33] Make anon_inodes unconditional [ver #11] [25/33] vfs: syscall: Add fsopen() to prepare for superblock creation [ver #11] [26/33] vfs: Implement logging through fs_context [ver #11] [27/33] vfs: Add some logging to the core users of the fs_context log [ver #11] [28/33] vfs: syscall: Add fsconfig() for configuring and managing a context [ver #11] [29/33] vfs: syscall: Add fsmount() to create a mount for a superblock [ver #11] [30/33] vfs: syscall: Add fspick() to select a superblock for reconfiguration [ver #11] [31/33] afs: Add fs_context support [ver #11] [32/33] afs: Use fs_context to pass parameters over automount [ver #11] [33/33] vfs: Add a sample program for the new mount API [ver #11]

diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl index ea1b413afd47..76d092b7d1b0 100644 --- a/arch/x86/entry/syscalls/syscall_32.tbl +++ b/arch/x86/entry/syscalls/syscall_32.tbl @@ -399,3 +399,4 @@ 385 i386 io_pgetevents sys_io_pgetevents __ia32_compat_sys_io_pgetevents 386 i386 rseq sys_rseq __ia32_sys_rseq 387 i386 open_tree sys_open_tree __ia32_sys_open_tree +388 i386 move_mount sys_move_mount __ia32_sys_move_mount diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl index 0545bed581dc..37ba4e65eee6 100644 --- a/arch/x86/entry/syscalls/syscall_64.tbl +++ b/arch/x86/entry/syscalls/syscall_64.tbl @@ -344,6 +344,7 @@ 333 common io_pgetevents __x64_sys_io_pgetevents 334 common rseq __x64_sys_rseq 335 common open_tree __x64_sys_open_tree +336 common move_mount __x64_sys_move_mount # # x32-specific system call numbers start at 512 to avoid cache impact diff --git a/fs/namespace.c b/fs/namespace.c index a4a01ecbcacd..e2934a4f342b 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2447,43 +2447,37 @@ static inline int tree_contains_unbindable(struct mount *mnt) return 0; } -static int do_move_mount(struct path *path, const char *old_name) +static int do_move_mount(struct path *old_path, struct path *new_path) { - struct path old_path, parent_path; + struct path parent_path = {.mnt = NULL, .dentry = NULL}; struct mount *p; struct mount *old; struct mountpoint *mp; int err; - if (!old_name || !*old_name) - return -EINVAL; - err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); - if (err) - return err; - mp = lock_mount(path); + mp = lock_mount(new_path); err = PTR_ERR(mp); if (IS_ERR(mp)) goto out; - old = real_mount(old_path.mnt); - p = real_mount(path->mnt); + old = real_mount(old_path->mnt); + p = real_mount(new_path->mnt); err = -EINVAL; if (!check_mnt(p) || !check_mnt(old)) goto out1; - if (old->mnt.mnt_flags & MNT_LOCKED) + if (!mnt_has_parent(old)) goto out1; - err = -EINVAL; - if (old_path.dentry != old_path.mnt->mnt_root) + if (old->mnt.mnt_flags & MNT_LOCKED) goto out1; - if (!mnt_has_parent(old)) + if (old_path->dentry != old_path->mnt->mnt_root) goto out1; - if (d_is_dir(path->dentry) != - d_is_dir(old_path.dentry)) + if (d_is_dir(new_path->dentry) != + d_is_dir(old_path->dentry)) goto out1; /* * Don't move a mount residing in a shared parent. @@ -2501,7 +2495,8 @@ static int do_move_mount(struct path *path, const char *old_name) if (p == old) goto out1; - err = attach_recursive_mnt(old, real_mount(path->mnt), mp, &parent_path); + err = attach_recursive_mnt(old, real_mount(new_path->mnt), mp, + &parent_path); if (err) goto out1; @@ -2513,6 +2508,22 @@ static int do_move_mount(struct path *path, const char *old_name) out: if (!err) path_put(&parent_path); + return err; +} + +static int do_move_mount_old(struct path *path, const char *old_name) +{ + struct path old_path; + int err; + + if (!old_name || !*old_name) + return -EINVAL; + + err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); + if (err) + return err; + + err = do_move_mount(&old_path, path); path_put(&old_path); return err; } @@ -2934,7 +2945,7 @@ long do_mount(const char *dev_name, const char __user *dir_name, else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) retval = do_change_type(&path, flags); else if (flags & MS_MOVE) - retval = do_move_mount(&path, dev_name); + retval = do_move_mount_old(&path, dev_name); else retval = do_new_mount(&path, type_page, sb_flags, mnt_flags, dev_name, data_page, data_size); @@ -3169,6 +3180,61 @@ SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, return ksys_mount(dev_name, dir_name, type, flags, data); } +/* + * Move a mount from one place to another. + * + * Note the flags value is a combination of MOVE_MOUNT_* flags. + */ +SYSCALL_DEFINE5(move_mount, + int, from_dfd, const char *, from_pathname, + int, to_dfd, const char *, to_pathname, + unsigned int, flags) +{ + struct path from_path, to_path; + unsigned int lflags; + int ret = 0; + + if (!may_mount()) + return -EPERM; + + if (flags & ~MOVE_MOUNT__MASK) + return -EINVAL; + + /* If someone gives a pathname, they aren't permitted to move + * from an fd that requires unmount as we can't get at the flag + * to clear it afterwards. + */ + lflags = 0; + if (flags & MOVE_MOUNT_F_SYMLINKS) lflags |= LOOKUP_FOLLOW; + if (flags & MOVE_MOUNT_F_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT; + if (flags & MOVE_MOUNT_F_EMPTY_PATH) lflags |= LOOKUP_EMPTY; + + ret = user_path_at(from_dfd, from_pathname, lflags, &from_path); + if (ret < 0) + return ret; + + lflags = 0; + if (flags & MOVE_MOUNT_T_SYMLINKS) lflags |= LOOKUP_FOLLOW; + if (flags & MOVE_MOUNT_T_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT; + if (flags & MOVE_MOUNT_T_EMPTY_PATH) lflags |= LOOKUP_EMPTY; + + ret = user_path_at(to_dfd, to_pathname, lflags, &to_path); + if (ret < 0) + goto out_from; + + ret = security_move_mount(&from_path, &to_path); + if (ret < 0) + goto out_to; + + ret = do_move_mount(&from_path, &to_path); + +out_to: + path_put(&to_path); +out_from: + path_put(&from_path); + return ret; +} + /* * Return true if path is reachable from root * diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index b43bbc893074..924424e7be8f 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -147,6 +147,10 @@ * Parse a string of security data filling in the opts structure * @options string containing all mount options known by the LSM * @opts binary data structure usable by the LSM + * @move_mount: + * Check permission before a mount is moved. + * @from_path indicates the mount that is going to be moved. + * @to_path indicates the mountpoint that will be mounted upon. * @dentry_init_security: * Compute a context for a dentry as the inode is not yet available * since NFSv4 has no label backed by an EA anyway. @@ -1480,6 +1484,7 @@ union security_list_options { unsigned long kern_flags, unsigned long *set_kern_flags); int (*sb_parse_opts_str)(char *options, struct security_mnt_opts *opts); + int (*move_mount)(const struct path *from_path, const struct path *to_path); int (*dentry_init_security)(struct dentry *dentry, int mode, const struct qstr *name, void **ctx, u32 *ctxlen); @@ -1811,6 +1816,7 @@ struct security_hook_heads { struct hlist_head sb_set_mnt_opts; struct hlist_head sb_clone_mnt_opts; struct hlist_head sb_parse_opts_str; + struct hlist_head move_mount; struct hlist_head dentry_init_security; struct hlist_head dentry_create_files_as; #ifdef CONFIG_SECURITY_PATH diff --git a/include/linux/security.h b/include/linux/security.h index 1498b9e0539b..9bb5bc6d596c 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -245,6 +245,7 @@ int security_sb_clone_mnt_opts(const struct super_block *oldsb, unsigned long kern_flags, unsigned long *set_kern_flags); int security_sb_parse_opts_str(char *options, struct security_mnt_opts *opts); +int security_move_mount(const struct path *from_path, const struct path *to_path); int security_dentry_init_security(struct dentry *dentry, int mode, const struct qstr *name, void **ctx, u32 *ctxlen); @@ -599,6 +600,12 @@ static inline int security_sb_parse_opts_str(char *options, struct security_mnt_ return 0; } +static inline int security_move_mount(const struct path *from_path, + const struct path *to_path) +{ + return 0; +} + static inline int security_inode_alloc(struct inode *inode) { return 0; diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index 3cc6b8f8bd2f..3c0855d9b105 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -901,6 +901,9 @@ asmlinkage long sys_statx(int dfd, const char __user *path, unsigned flags, asmlinkage long sys_rseq(struct rseq __user *rseq, uint32_t rseq_len, int flags, uint32_t sig); asmlinkage long sys_open_tree(int dfd, const char __user *path, unsigned flags); +asmlinkage long sys_move_mount(int from_dfd, const char __user *from_path, + int to_dfd, const char __user *to_path, + unsigned int ms_flags); /* * Architecture-specific system calls diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h index e8db2911adca..89adf0d731ab 100644 --- a/include/uapi/linux/mount.h +++ b/include/uapi/linux/mount.h @@ -7,4 +7,15 @@ #define OPEN_TREE_CLONE 1 /* Clone the target tree and attach the clone */ #define OPEN_TREE_CLOEXEC O_CLOEXEC /* Close the file on execve() */ +/* + * move_mount() flags. + */ +#define MOVE_MOUNT_F_SYMLINKS 0x00000001 /* Follow symlinks on from path */ +#define MOVE_MOUNT_F_AUTOMOUNTS 0x00000002 /* Follow automounts on from path */ +#define MOVE_MOUNT_F_EMPTY_PATH 0x00000004 /* Empty from path permitted */ +#define MOVE_MOUNT_T_SYMLINKS 0x00000010 /* Follow symlinks on to path */ +#define MOVE_MOUNT_T_AUTOMOUNTS 0x00000020 /* Follow automounts on to path */ +#define MOVE_MOUNT_T_EMPTY_PATH 0x00000040 /* Empty to path permitted */ +#define MOVE_MOUNT__MASK 0x00000077 + #endif /* _UAPI_LINUX_MOUNT_H */ diff --git a/security/security.c b/security/security.c index 7cafc1c90d16..5149c2cbe8a7 100644 --- a/security/security.c +++ b/security/security.c @@ -439,6 +439,11 @@ int security_sb_parse_opts_str(char *options, struct security_mnt_opts *opts) } EXPORT_SYMBOL(security_sb_parse_opts_str); +int security_move_mount(const struct path *from_path, const struct path *to_path) +{ + return call_int_hook(move_mount, 0, from_path, to_path); +} + int security_inode_alloc(struct inode *inode) { inode->i_security = NULL;

[02/33] vfs: syscall: Add move_mount(2) to move mounts around [ver #11]

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