[PATCH 3/9] VFS: Introduce a mount context
From: David Howells
Date: Wed May 03 2017 - 12:07:59 EST
Introduce a mount context concept. This is allocated at the beginning of
the mount procedure and into it is placed:
(1) Filesystem type.
(2) Namespaces.
(3) Device name.
(4) Superblock flags (MS_*) and mount flags (MNT_*).
(5) Security details.
(6) Filesystem-specific data, as set by the mount options.
It also gives a place in which to hang an error message for later retrieval
(see the mount-by-fd syscall later in this series).
Rather than calling fs_type->mount(), a mount_context struct is created and
fs_type->fsopen() is called to set it up. fs_type->mc_size says how much
should be added on to the mount context for the filesystem's use.
A set of operations have to be set by ->fsopen() to provide freeing,
duplication, option parsing, binary data parsing, validation, mounting and
superblock filling.
It should be noted that, whilst this patch adds a lot of lines of code,
there is quite a bit of duplication with existing code that can be
eliminated should all filesystems be converted over.
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---
Documentation/filesystems/mounting.txt | 445 ++++++++++++++++++++++++++++++++
fs/Makefile | 3
fs/internal.h | 2
fs/mount.h | 3
fs/mount_context.c | 343 +++++++++++++++++++++++++
fs/namespace.c | 270 +++++++++++++++++--
fs/super.c | 50 +++-
include/linux/fs.h | 11 +
include/linux/lsm_hooks.h | 37 +++
include/linux/mount.h | 67 +++++
include/linux/security.h | 29 ++
security/security.c | 32 ++
security/selinux/hooks.c | 179 +++++++++++++
13 files changed, 1435 insertions(+), 36 deletions(-)
create mode 100644 Documentation/filesystems/mounting.txt
create mode 100644 fs/mount_context.c
diff --git a/Documentation/filesystems/mounting.txt b/Documentation/filesystems/mounting.txt
new file mode 100644
index 000000000000..a942ccd08376
--- /dev/null
+++ b/Documentation/filesystems/mounting.txt
@@ -0,0 +1,445 @@
+ ===================
+ FILESYSTEM MOUNTING
+ ===================
+
+CONTENTS
+
+ (1) Overview.
+
+ (2) The mount context.
+
+ (3) The mount context operations.
+
+ (4) Mount context security.
+
+ (5) VFS mount context operations.
+
+
+========
+OVERVIEW
+========
+
+The creation of new mounts is now to be done in a multistep process:
+
+ (1) Create a mount context.
+
+ (2) Parse the options and attach them to the mount context. Options may be
+ passed individually from userspace.
+
+ (3) Validate and pre-process the mount context.
+
+ (4) Perform the mount.
+
+ (5) Return an error message attached to the mount context.
+
+ (6) Destroy the mount context.
+
+To support this, the file_system_type struct gains two new fields:
+
+ unsigned short mc_size;
+
+which indicates how much space the filesystem would like tacked onto the end of
+the mount_context struct for its own purposes, and:
+
+ int (*fsopen)(struct mount_context *mc, struct super_block *src_sb);
+
+which is invoked to set up the filesystem-specific parts of a mount context,
+including the additional space. The src_sb parameter is used to convey the
+superblock from which the filesystem may draw extra information (such as
+namespaces), for submount (MS_SUBMOUNT) or remount (MS_REMOUNT) purposes or it
+will be NULL.
+
+Note that security initialisation is done *after* the filesystem is called so
+that the namespaces may be adjusted first.
+
+And the super_operations struct gains one:
+
+ int (*remount_fs_mc) (struct super_block *, struct mount_context *);
+
+This shadows the ->remount_fs() operation and takes a prepared mount context
+instead of the mount flags and data page. It may modify the ms_flags in the
+context for the caller to pick up.
+
+[NOTE] remount_fs_mc is intended as a replacement for remount_fs.
+
+
+=================
+THE MOUNT CONTEXT
+=================
+
+The mount process is governed by a mount context. This is represented by the
+mount_context structure:
+
+ struct mount_context {
+ const struct mount_context_operations *ops;
+ struct file_system_type *fs;
+ struct user_namespace *user_ns;
+ struct mnt_namespace *mnt_ns;
+ struct pid_namespace *pid_ns;
+ struct net *net_ns;
+ const struct cred *cred;
+ char *device;
+ char *root_path;
+ void *security;
+ const char *error;
+ unsigned int ms_flags;
+ unsigned int mnt_flags;
+ bool mounted;
+ bool sloppy;
+ bool silent;
+ enum mount_type mount_type : 8;
+ };
+
+When allocated, the mount_context struct is extended by ->mc_size bytes as
+specified by the specified file_system_type struct. This is for use by the
+filesystem. The filesystem should wrap the struct in its own, e.g.:
+
+ struct nfs_mount_context {
+ struct mount_context mc;
+ ...
+ };
+
+placing the mount_context struct first. container_of() can then be used.
+
+The mount_context fields are as follows:
+
+ (*) const struct mount_context_operations *ops
+
+ These are operations that can be done on a mount context. See below.
+ This must be set by the ->fsopen() file_system_type operation.
+
+ (*) struct file_system_type *fs
+
+ A pointer to the file_system_type of the filesystem that is being
+ mounted. This retains a ref on the type owner.
+
+ (*) struct user_namespace *user_ns
+ (*) struct mnt_namespace *mnt_ns
+ (*) struct pid_namespace *pid_ns
+ (*) struct net *net_ns
+
+ This is a subset of the namespaces in use by the invoking process. This
+ retains a ref on each namespace. The subscribed namespaces may be
+ replaced by the filesystem to reflect other sources, such as the parent
+ mount superblock on an automount.
+
+ (*) struct cred *cred
+
+ The mounter's credentials. This retains a ref on the credentials.
+
+ (*) char *device
+
+ This is the device to be mounted. It may be a block device
+ (e.g. /dev/sda1) or something more exotic, such as the "host:/path" that
+ NFS desires.
+
+ (*) char *root_path
+
+ A path to the place inside the filesystem to actually mount. This allows
+ a mount and bind-mount to be combined.
+
+ [NOTE] This isn't implemented yet, but NFS has the code to do this which
+ could be moved to the VFS.
+
+ (*) void *security
+
+ A place for the LSMs to hang their security data for the mount. The
+ relevant security operations are described below.
+
+ (*) const char *error
+
+ A place for the VFS and the filesystem to hang an error message. This
+ should be in the form of a static string that doesn't need deallocation
+ and the pointer to which can just be overwritten. Under some
+ circumstances, this can be retrieved by userspace.
+
+ Note that the existence of the error string is expected to be guaranteed
+ by the reference on the file_system_type object held by ->fs or any
+ filesystem-specific reference held in the filesystem context until the
+ ->free() operation is called.
+
+ (*) unsigned int ms_flags
+ (*) unsigned int mnt_flags
+
+ These hold the mount flags. ms_flags holds MS_* flags and mnt_flags holds
+ MNT_* flags.
+
+ (*) bool mounted
+
+ This is set to true once a mount attempt is made. This causes an error to
+ be given on subsequent mount attempts with the same context and prevents
+ multiple mount attempts.
+
+ (*) bool sloppy
+ (*) bool silent
+
+ These are set if the sloppy or silent mount options are given.
+
+ [NOTE] sloppy is probably unnecessary when userspace passes over one
+ option at a time since the error can just be ignored if userspace deems it
+ to be unimportant.
+
+ [NOTE] silent is probably redundant with ms_flags & MS_SILENT.
+
+ (*) enum mount_type
+
+ This indicates the type of mount operation. The available values are:
+
+ MOUNT_TYPE_NEW -- New mount
+ MOUNT_TYPE_SUBMOUNT -- New automatic submount of extant mount
+ MOUNT_TYPE_REMOUNT -- Change an existing mount
+
+The mount context is created by calling __vfs_fsopen(), vfs_fsopen(),
+vfs_mntopen() or vfs_dup_mount_context() and is destroyed with
+put_mount_context(). Note that the structure is not refcounted.
+
+VFS, security and filesystem mount options are set individually with
+vfs_mount_option() or in bulk with generic_monolithic_mount_data().
+
+When mounting, the filesystem is allowed to take data from any of the pointers
+and attach it to the superblock (or whatever), provided it clears the pointer
+in the mount context.
+
+The filesystem is also allowed to allocate resources and pin them with the
+mount context. For instance, NFS might pin the appropriate protocol version
+module.
+
+
+============================
+THE MOUNT CONTEXT OPERATIONS
+============================
+
+The mount context points to a table of operations:
+
+ struct mount_context_operations {
+ void (*free)(struct mount_context *mc);
+ int (*dup)(struct mount_context *mc, struct mount_context *src);
+ int (*option)(struct mount_context *mc, char *p);
+ int (*monolithic_mount_data)(struct mount_context *mc, void *data);
+ int (*validate)(struct mount_context *mc);
+ struct dentry *(*mount)(struct mount_context *mc);
+ int (*fill_super)(struct super_block *s, struct mount_context *mc);
+ };
+
+These operations are invoked by the various stages of the mount procedure to
+manage the mount context. They are as follows:
+
+ (*) void (*free)(struct mount_context *mc);
+
+ Called to clean up the filesystem-specific part of the mount context when
+ the context is destroyed. It should be aware that parts of the context
+ may have been removed and NULL'd out by ->mount().
+
+ (*) int (*dup)(struct mount_context *mc, struct mount_context *src);
+
+ Called when a mount context has been duplicated to get any refs or copy
+ any non-referenced resources held in the filesystem-specific part of the
+ mount context. An error may be returned to indicate failure to do this.
+
+ [!] Note that if this fails, put_mount_context() will be called
+ immediately thereafter, so ->dup() *must* make the
+ filesystem-specific part safe for ->free().
+
+ (*) int (*option)(struct mount_context *mc, char *p);
+
+ Called when an option is to be added to the mount context. p points to
+ the option string, likely in "key[=val]" format. VFS-specific options
+ will have been weeded out and mc->ms_flags and mc->mnt_flags updated in
+ the context. Security options will also have been weeded out and
+ mc->security updated.
+
+ If successful, 0 should be returned and a negative error code otherwise.
+ If an ambiguous error (such as -EINVAL) is returned, mc->error should be
+ set in the context to a string that provides more information.
+
+ (*) int (*monolithic_mount_data)(struct mount_context *mc, void *data);
+
+ Called when the mount(2) system call is invoked to pass the entire data
+ page in one go. If this is expected to be just a list of "key[=val]"
+ items separated by commas, then this may be set to NULL.
+
+ The return value is as for ->option().
+
+ If the filesystem (eg. NFS) needs to examine the data first and then
+ finds it's the standard key-val list then it may pass it off to:
+
+ int generic_monolithic_mount_data(struct mount_context *mc, void *data);
+
+ (*) int (*validate)(struct mount_context *mc);
+
+ Called when all the options have been applied and the mount is about to
+ take place. It is should check for inconsistencies from mount options
+ and it is also allowed to do preliminary resource acquisition. For
+ instance, the core NFS module could load the NFS protocol module here.
+
+ Note that if mc->mount_type == MOUNT_TYPE_REMOUNT, some of the options
+ necessary for a new mount may not be set.
+
+ The return value is as for ->option().
+
+ (*) struct dentry *(*mount)(struct mount_context *mc);
+
+ Called to effect a new mount or new submount using the information stored
+ in the mount context (remounts go via a different vector). It may detach
+ any resources it desires from the mount context and transfer them to the
+ superblock it creates.
+
+ On success it should return the dentry that's at the root of the mount.
+ In future, mc->root_path will then be applied to this.
+
+ In the case of an error, it should return a negative error code and set
+ mc->error.
+
+ (*) int (*fill_super)(struct super_block *s, struct mount_context *mc);
+
+ This is available to be used by things like mount_ns_mc() that are called
+ by ->mount() to transfer information/resources from the mount context to
+ the superblock.
+
+
+======================
+MOUNT CONTEXT SECURITY
+======================
+
+The mount context contains a security points that the LSMs can use for
+building up a security context for the superblock to be mounted. There are a
+number of operations used by the new mount code for this purpose:
+
+ (*) int security_mount_ctx_alloc(struct mount_context *mc,
+ struct super_block *src_sb);
+
+ Called to initialise mc->security (which is preset to NULL) and allocate
+ any resources needed. It should return 0 on success and a negative error
+ code on failure.
+
+ src_sb is non-NULL in the case of a remount (MS_REMOUNT) in which case it
+ indicates the superblock to be remounted or in the case of a submount
+ (MS_SUBMOUNT) in which case it indicates the parent superblock.
+
+ (*) int security_mount_ctx_dup(struct mount_context *mc,
+ struct mount_context *src_mc);
+
+ Called to initialise mc->security (which is preset to NULL) and allocate
+ any resources needed. The original mount context is pointed to by src_mc
+ and may be used for reference. It should return 0 on success and a
+ negative error code on failure.
+
+ (*) void security_mount_ctx_free(struct mount_context *mc);
+
+ Called to clean up anything attached to mc->security. Note that the
+ contents may have been transferred to a superblock and the pointer NULL'd
+ out during mount.
+
+ (*) int security_mount_ctx_option(struct mount_context *mc, char *opt);
+
+ Called for each mount option. The mount options are in "key[=val]"
+ form. An active LSM may reject one with an error, pass one over and
+ return 0 or consume one and return 1. If consumed, the option isn't
+ passed on to the filesystem.
+
+ If it returns an error, it should set mc->error if the error is
+ ambiguous.
+
+ (*) int security_mount_ctx_kern_mount(struct mount_context *mc,
+ struct super_block *sb);
+
+ Called during mount to verify that the specified superblock is allowed to
+ be mounted and to transfer the security data there.
+
+ On success, it should return 0; otherwise it should return an error and
+ set mc->error to indicate the problem. It should not return -ENOMEM as
+ this should be taken care of in advance.
+
+ [NOTE] Should I add a security_mount_ctx_validate() operation so that the
+ LSM has the opportunity to allocate stuff and check the options as a
+ whole?
+
+
+============================
+VFS MOUNT CONTEXT OPERATIONS
+============================
+
+There are four operations for creating a mount context and one for destroying
+a context:
+
+ (*) struct mount_context *__vfs_fsopen(struct file_system_type *fs_type,
+ struct super_block *src_sb;
+ unsigned int ms_flags,
+ unsigned int mnt_flags);
+
+ Create a mount context given a filesystem type pointer. This allocates
+ the mount context, sets the flags, initialises the security and calls
+ fs_type->fsopen() to initialise the filesystem context.
+
+ src_sb can be NULL or it may indicate a superblock that is going to be
+ remounted (MS_REMOUNT) or a superblock that is the parent of a submount
+ (MS_SUBMOUNT). This superblock is provided as a source of namespace
+ information.
+
+ (*) struct mount_context *vfs_mntopen(struct vfsmount *mnt,
+ unsigned int ms_flags,
+ unsigned int mnt_flags);
+
+ Create a mount context from the same filesystem as an extant mount and
+ initialise the mount parameters from the superblock underlying that
+ mount. This is used by remount.
+
+ (*) struct mount_context *vfs_fsopen(const char *fs_name);
+
+ Create a mount context given a filesystem name. It is assumed that the
+ mount flags will be passed in as text options later. This is intended to
+ be called from sys_fsopen(). This copies current's namespaces to the
+ mount context.
+
+ (*) struct mount_context *vfs_dup_mount_context(struct mount_context *src);
+
+ Duplicate a mount context, copying any options noted and duplicating or
+ additionally referencing any resources held therein. This is available
+ for use where a filesystem has to get a mount within a mount, such as
+ NFS4 does by internally mounting the root of the target server and then
+ doing a private pathwalk to the target directory.
+
+ (*) void put_mount_context(struct mount_context *ctx);
+
+ Destroy a mount context, releasing any resources it holds. This calls
+ the ->free() operation. This is intended to be called by anyone who
+ created a mount context.
+
+ [!] Mount contexts are not refcounted, so this causes unconditional
+ destruction.
+
+In all the above operations, apart from the put op, the return is a mount
+context pointer or a negative error code. No error string is saved as the
+error string is only guaranteed as long as the file_system_type is pinned (and
+thus the module).
+
+In the remaining operations, if an error occurs, a negative error code is
+returned and, if not obvious, mc->error should be set to point to a useful
+string. The string should not be freed.
+
+ (*) struct vfsmount *vfs_kern_mount_mc(struct mount_context *mc);
+
+ Create a mount given the parameters in the specified mount context. This
+ invokes the ->validate() op and then the ->mount() op.
+
+ (*) struct vfsmount *vfs_submount_mc(const struct dentry *mountpoint,
+ struct mount_context *mc);
+
+ Create a mount given a mount context and set MS_SUBMOUNT on it. A
+ wrapper around vfs_kern_mount_mc(). This is intended to be called from
+ filesystems that have automount points (NFS, AFS, ...).
+
+ (*) int vfs_mount_option(struct mount_context *mc, char *data);
+
+ Supply a single mount option to the mount context. The mount option
+ should likely be in a "key[=val]" string form. The option is first
+ checked to see if it corresponds to a standard mount flag (in which case
+ it is used to mark an MS_xxx flag and consumed) or a security option (in
+ which case the LSM consumes it) before it is passed on to the filesystem.
+
+ (*) int generic_monolithic_mount_data(struct mount_context *ctx, void *data);
+
+ Parse a sys_mount() data page, assuming the form to be a text list
+ consisting of key[=val] options separated by commas. Each item in the
+ list is passed to vfs_mount_option(). This is the default when the
+ ->monolithic_mount_data() operation is NULL.
diff --git a/fs/Makefile b/fs/Makefile
index 7bbaca9c67b1..308a104a9a07 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -11,7 +11,8 @@ obj-y := open.o read_write.o file_table.o super.o \
attr.o bad_inode.o file.o filesystems.o namespace.o \
seq_file.o xattr.o libfs.o fs-writeback.o \
pnode.o splice.o sync.o utimes.o \
- stack.o fs_struct.o statfs.o fs_pin.o nsfs.o
+ stack.o fs_struct.o statfs.o fs_pin.o nsfs.o \
+ mount_context.o
ifeq ($(CONFIG_BLOCK),y)
obj-y += buffer.o block_dev.o direct-io.o mpage.o
diff --git a/fs/internal.h b/fs/internal.h
index 076751d90ba2..ef8c5e93f364 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -87,7 +87,7 @@ extern struct file *get_empty_filp(void);
/*
* super.c
*/
-extern int do_remount_sb(struct super_block *, int, void *, int);
+extern int do_remount_sb(struct super_block *, int, void *, int, struct mount_context *);
extern bool trylock_super(struct super_block *sb);
extern struct dentry *mount_fs(struct file_system_type *,
int, const char *, void *);
diff --git a/fs/mount.h b/fs/mount.h
index 2826543a131d..b1e99b38f2ee 100644
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -108,9 +108,10 @@ static inline void detach_mounts(struct dentry *dentry)
__detach_mounts(dentry);
}
-static inline void get_mnt_ns(struct mnt_namespace *ns)
+static inline struct mnt_namespace *get_mnt_ns(struct mnt_namespace *ns)
{
atomic_inc(&ns->count);
+ return ns;
}
extern seqlock_t mount_lock;
diff --git a/fs/mount_context.c b/fs/mount_context.c
new file mode 100644
index 000000000000..7d765c100bf1
--- /dev/null
+++ b/fs/mount_context.c
@@ -0,0 +1,343 @@
+/* Provide a way to create a mount context within the kernel that can be
+ * configured before mounting.
+ *
+ * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@xxxxxxxxxx)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include <linux/fs.h>
+#include <linux/mount.h>
+#include <linux/nsproxy.h>
+#include <linux/slab.h>
+#include <linux/magic.h>
+#include <linux/security.h>
+#include <linux/parser.h>
+#include <linux/mnt_namespace.h>
+#include <linux/pid_namespace.h>
+#include <linux/user_namespace.h>
+#include <net/net_namespace.h>
+#include "mount.h"
+
+static const match_table_t common_set_mount_options = {
+ { MS_DIRSYNC, "dirsync" },
+ { MS_I_VERSION, "iversion" },
+ { MS_LAZYTIME, "lazytime" },
+ { MS_MANDLOCK, "mand" },
+ { MS_NOATIME, "noatime" },
+ { MS_NODEV, "nodev" },
+ { MS_NODIRATIME, "nodiratime" },
+ { MS_NOEXEC, "noexec" },
+ { MS_NOSUID, "nosuid" },
+ { MS_POSIXACL, "posixacl" },
+ { MS_RDONLY, "ro" },
+ { MS_REC, "rec" },
+ { MS_RELATIME, "relatime" },
+ { MS_STRICTATIME, "strictatime" },
+ { MS_SYNCHRONOUS, "sync" },
+ { MS_VERBOSE, "verbose" },
+ { },
+};
+
+static const match_table_t common_clear_mount_options = {
+ { MS_LAZYTIME, "nolazytime" },
+ { MS_MANDLOCK, "nomand" },
+ { MS_NODEV, "dev" },
+ { MS_NOEXEC, "exec" },
+ { MS_NOSUID, "suid" },
+ { MS_RDONLY, "rw" },
+ { MS_RELATIME, "norelatime" },
+ { MS_SILENT, "silent" },
+ { MS_STRICTATIME, "nostrictatime" },
+ { MS_SYNCHRONOUS, "async" },
+ { },
+};
+
+static const match_table_t forbidden_mount_options = {
+ { MS_BIND, "bind" },
+ { MS_KERNMOUNT, "ro" },
+ { MS_MOVE, "move" },
+ { MS_PRIVATE, "private" },
+ { MS_REMOUNT, "remount" },
+ { MS_SHARED, "shared" },
+ { MS_SLAVE, "slave" },
+ { MS_UNBINDABLE, "unbindable" },
+ { },
+};
+
+/*
+ * Check for a common mount option.
+ */
+static noinline int vfs_common_mount_option(struct mount_context *mc, char *data)
+{
+ substring_t args[MAX_OPT_ARGS];
+ unsigned int token;
+
+ token = match_token(data, common_set_mount_options, args);
+ if (token) {
+ mc->ms_flags |= token;
+ return 1;
+ }
+
+ token = match_token(data, common_clear_mount_options, args);
+ if (token) {
+ mc->ms_flags &= ~token;
+ return 1;
+ }
+
+ token = match_token(data, forbidden_mount_options, args);
+ if (token) {
+ mc->error = "Mount option, not superblock option";
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+/**
+ * vfs_mount_option - Add a single mount option to a mount context
+ * @mc: The mount context to modify
+ * @option: The option to apply.
+ *
+ * A single mount option in string form is applied to the mount being set up in
+ * the mount context. Certain standard options (for example "ro") are
+ * translated into flag bits without going to the filesystem. The active
+ * security module allowed to observe and poach options. Any other options are
+ * passed over to the filesystem to parse.
+ *
+ * This may be called multiple times for a context.
+ *
+ * Returns 0 on success and a negative error code on failure. In the event of
+ * failure, mc->error may have been set to a non-allocated string that gives
+ * more information.
+ */
+int vfs_mount_option(struct mount_context *mc, char *data)
+{
+ int ret;
+
+ if (mc->mounted)
+ return -EBUSY;
+
+ ret = vfs_common_mount_option(mc, data);
+ if (ret < 0)
+ return ret;
+ if (ret == 1)
+ return 0;
+
+ ret = security_mount_ctx_option(mc, data);
+ if (ret < 0)
+ return ret;
+ if (ret == 1)
+ return 0;
+
+ return mc->ops->option(mc, data);
+}
+EXPORT_SYMBOL(vfs_mount_option);
+
+/**
+ * generic_monolithic_mount_data - Parse key[=val][,key[=val]]* mount data
+ * @mc: The mount context to populate
+ * @data: The data to parse
+ *
+ * Parse a blob of data that's in key[=val][,key[=val]]* form. This can be
+ * called from the ->monolithic_mount_data() mount context operation.
+ *
+ * Returns 0 on success or the error returned by the ->option() mount context
+ * operation on failure.
+ */
+int generic_monolithic_mount_data(struct mount_context *ctx, void *data)
+{
+ char *options = data, *p;
+ int ret;
+
+ if (!options)
+ return 0;
+
+ while ((p = strsep(&options, ",")) != NULL) {
+ if (*p) {
+ ret = vfs_mount_option(ctx, p);
+ if (ret < 0)
+ return ret;
+ }
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(generic_monolithic_mount_data);
+
+/**
+ * __vfs_fsopen - Open a filesystem and create a mount context
+ * @fs_type: The filesystem type
+ * @src_sb: A superblock from which this one derives (or NULL)
+ * @ms_flags: Superblock flags and op flags (such as MS_REMOUNT)
+ * @mnt_flags: Mountpoint flags, such as MNT_READONLY
+ * @mount_type: Type of mount
+ *
+ * Open a filesystem and create a mount context. The mount context is
+ * initialised with the supplied flags and, if a submount/automount from
+ * another superblock (@src_sb), may have parameters such as namespaces copied
+ * across from that superblock.
+ */
+struct mount_context *__vfs_fsopen(struct file_system_type *fs_type,
+ struct super_block *src_sb,
+ unsigned int ms_flags, unsigned int mnt_flags,
+ enum mount_type mount_type)
+{
+ struct mount_context *mc;
+ int ret;
+
+ if (fs_type->fsopen && fs_type->mc_size < sizeof(*mc))
+ BUG();
+
+ mc = kzalloc(max_t(size_t, fs_type->mc_size, sizeof(*mc)), GFP_KERNEL);
+ if (!mc)
+ return ERR_PTR(-ENOMEM);
+
+ mc->mount_type = mount_type;
+ mc->ms_flags = ms_flags;
+ mc->mnt_flags = mnt_flags;
+ mc->fs_type = fs_type;
+ get_filesystem(fs_type);
+ mc->mnt_ns = get_mnt_ns(current->nsproxy->mnt_ns);
+ mc->pid_ns = get_pid_ns(task_active_pid_ns(current));
+ mc->net_ns = get_net(current->nsproxy->net_ns);
+ mc->user_ns = get_user_ns(current_user_ns());
+ mc->cred = get_current_cred();
+
+
+ /* TODO: Make all filesystems support this unconditionally */
+ if (mc->fs_type->fsopen) {
+ ret = mc->fs_type->fsopen(mc, src_sb);
+ if (ret < 0)
+ goto err_mc;
+ }
+
+ /* Do the security check last because ->fsopen may change the
+ * namespace subscriptions.
+ */
+ ret = security_mount_ctx_alloc(mc, src_sb);
+ if (ret < 0)
+ goto err_mc;
+
+ return mc;
+
+err_mc:
+ put_mount_context(mc);
+ return ERR_PTR(ret);
+}
+EXPORT_SYMBOL(__vfs_fsopen);
+
+/**
+ * vfs_fsopen - Open a filesystem and create a mount context
+ * @fs_name: The name of the filesystem
+ *
+ * Open a filesystem and create a mount context that will hold the mount
+ * options, device name, security details, etc.. Note that the caller should
+ * check the ->ops pointer in the returned context to determine whether the
+ * filesystem actually supports the mount context itself.
+ */
+struct mount_context *vfs_fsopen(const char *fs_name)
+{
+ struct file_system_type *fs_type;
+ struct mount_context *mc;
+
+ fs_type = get_fs_type(fs_name);
+ if (!fs_type)
+ return ERR_PTR(-ENODEV);
+
+ mc = __vfs_fsopen(fs_type, NULL, 0, 0, MOUNT_TYPE_NEW);
+ put_filesystem(fs_type);
+ return mc;
+}
+EXPORT_SYMBOL(vfs_fsopen);
+
+/**
+ * vfs_mntopen - Create a mount context and initialise it from an extant mount
+ * @mnt: The mountpoint to open
+ * @ms_flags: Superblock flags and op flags (such as MS_REMOUNT)
+ * @mnt_flags: Mountpoint flags, such as MNT_READONLY
+ * @mount_type: Type of mount
+ *
+ * Open a mounted filesystem and create a mount context such that a remount can
+ * be effected.
+ */
+struct mount_context *vfs_mntopen(struct vfsmount *mnt,
+ unsigned int ms_flags,
+ unsigned int mnt_flags,
+ enum mount_type mount_type)
+{
+ return __vfs_fsopen(mnt->mnt_sb->s_type, mnt->mnt_sb,
+ ms_flags, mnt_flags, mount_type);
+}
+
+/**
+ * vfs_dup_mount_context: Duplicate a mount context.
+ * @src: The mount context to copy.
+ */
+struct mount_context *vfs_dup_mount_context(struct mount_context *src)
+{
+ struct mount_context *mc;
+ int ret;
+
+ if (!src->ops->dup)
+ return ERR_PTR(-ENOTSUPP);
+
+ mc = kmemdup(src, src->fs_type->mc_size, GFP_KERNEL);
+ if (!mc)
+ return ERR_PTR(-ENOMEM);
+
+ mc->device = NULL;
+ mc->root_path = NULL;
+ mc->security = NULL;
+ mc->error = NULL;
+ get_filesystem(mc->fs_type);
+ get_mnt_ns(mc->mnt_ns);
+ get_pid_ns(mc->pid_ns);
+ get_net(mc->net_ns);
+ get_user_ns(mc->user_ns);
+ get_cred(mc->cred);
+
+ /* Can't call put until we've called ->dup */
+ ret = mc->ops->dup(mc, src);
+ if (ret < 0)
+ goto err_mc;
+
+ ret = security_mount_ctx_dup(mc, src);
+ if (ret < 0)
+ goto err_mc;
+ return mc;
+
+err_mc:
+ put_mount_context(mc);
+ return ERR_PTR(ret);
+}
+EXPORT_SYMBOL(vfs_dup_mount_context);
+
+/*
+ * Dispose of a mount context.
+ */
+void put_mount_context(struct mount_context *mc)
+{
+ if (mc->ops && mc->ops->free)
+ mc->ops->free(mc);
+ security_mount_ctx_free(mc);
+ if (mc->mnt_ns)
+ put_mnt_ns(mc->mnt_ns);
+ if (mc->pid_ns)
+ put_pid_ns(mc->pid_ns);
+ if (mc->net_ns)
+ put_net(mc->net_ns);
+ put_user_ns(mc->user_ns);
+ if (mc->cred)
+ put_cred(mc->cred);
+ put_filesystem(mc->fs_type);
+ kfree(mc->device);
+ kfree(mc->root_path);
+ kfree(mc);
+}
+EXPORT_SYMBOL(put_mount_context);
diff --git a/fs/namespace.c b/fs/namespace.c
index db034b6afd43..e0edab9af308 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -25,6 +25,7 @@
#include <linux/magic.h>
#include <linux/bootmem.h>
#include <linux/task_work.h>
+#include <linux/file.h>
#include <linux/sched/task.h>
#include "pnode.h"
@@ -783,9 +784,14 @@ static void put_mountpoint(struct mountpoint *mp)
}
}
+static inline int __check_mnt(struct mount *mnt, struct mnt_namespace *mnt_ns)
+{
+ return mnt->mnt_ns == mnt_ns;
+}
+
static inline int check_mnt(struct mount *mnt)
{
- return mnt->mnt_ns == current->nsproxy->mnt_ns;
+ return __check_mnt(mnt, current->nsproxy->mnt_ns);
}
/*
@@ -1596,7 +1602,7 @@ static int do_umount(struct mount *mnt, int flags)
return -EPERM;
down_write(&sb->s_umount);
if (!(sb->s_flags & MS_RDONLY))
- retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
+ retval = do_remount_sb(sb, MS_RDONLY, NULL, 0, NULL);
up_write(&sb->s_umount);
return retval;
}
@@ -2279,6 +2285,26 @@ static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
}
/*
+ * Parse the monolithic page of mount data given to sys_mount().
+ */
+static int parse_monolithic_mount_data(struct mount_context *mc, void *data)
+{
+ int (*monolithic_mount_data)(struct mount_context *, void *);
+ int ret;
+
+ monolithic_mount_data = mc->ops->monolithic_mount_data;
+ if (!monolithic_mount_data)
+ monolithic_mount_data = generic_monolithic_mount_data;
+
+ ret = monolithic_mount_data(mc, data);
+ if (ret < 0)
+ return ret;
+ if (mc->ops->validate)
+ return mc->ops->validate(mc);
+ return 0;
+}
+
+/*
* change filesystem flags. dir should be a physical root of filesystem.
* If you've mounted a non-root directory somewhere and want to do remount
* on it - tough luck.
@@ -2286,13 +2312,14 @@ static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
static int do_remount(struct path *path, int flags, int mnt_flags,
void *data)
{
+ struct mount_context *mc = NULL;
int err;
struct super_block *sb = path->mnt->mnt_sb;
struct mount *mnt = real_mount(path->mnt);
+ struct file_system_type *type = sb->s_type;
if (!check_mnt(mnt))
return -EINVAL;
-
if (path->dentry != path->mnt->mnt_root)
return -EINVAL;
@@ -2323,9 +2350,19 @@ static int do_remount(struct path *path, int flags, int mnt_flags,
return -EPERM;
}
- err = security_sb_remount(sb, data);
- if (err)
- return err;
+ if (type->fsopen) {
+ mc = vfs_mntopen(path->mnt, flags, mnt_flags, MOUNT_TYPE_REMOUNT);
+ if (IS_ERR(mc))
+ return PTR_ERR(mc);
+
+ err = parse_monolithic_mount_data(mc, data);
+ if (err < 0)
+ goto err_mc;
+ } else {
+ err = security_sb_remount(sb, data);
+ if (err)
+ return err;
+ }
down_write(&sb->s_umount);
if (flags & MS_BIND)
@@ -2333,7 +2370,7 @@ static int do_remount(struct path *path, int flags, int mnt_flags,
else if (!capable(CAP_SYS_ADMIN))
err = -EPERM;
else
- err = do_remount_sb(sb, flags, data, 0);
+ err = do_remount_sb(sb, flags, data, 0, mc);
if (!err) {
lock_mount_hash();
mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK;
@@ -2342,6 +2379,9 @@ static int do_remount(struct path *path, int flags, int mnt_flags,
unlock_mount_hash();
}
up_write(&sb->s_umount);
+err_mc:
+ if (mc)
+ put_mount_context(mc);
return err;
}
@@ -2451,7 +2491,8 @@ static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
/*
* add a mount into a namespace's mount tree
*/
-static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags)
+static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags,
+ struct mnt_namespace *mnt_ns)
{
struct mountpoint *mp;
struct mount *parent;
@@ -2465,7 +2506,7 @@ static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags)
parent = real_mount(path->mnt);
err = -EINVAL;
- if (unlikely(!check_mnt(parent))) {
+ if (unlikely(!__check_mnt(parent, mnt_ns))) {
/* that's acceptable only for automounts done in private ns */
if (!(mnt_flags & MNT_SHRINKABLE))
goto unlock;
@@ -2493,42 +2534,73 @@ static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags)
}
static bool mount_too_revealing(struct vfsmount *mnt, int *new_mnt_flags);
+static int do_new_mount_mc(struct mount_context *mc, struct path *mountpoint,
+ unsigned int mnt_flags);
/*
* create a new mount for userspace and request it to be added into the
* namespace's tree
*/
-static int do_new_mount(struct path *path, const char *fstype, int flags,
+static int do_new_mount(struct path *mountpoint, const char *fstype, int flags,
int mnt_flags, const char *name, void *data)
{
- struct file_system_type *type;
+ struct mount_context *mc;
struct vfsmount *mnt;
int err;
if (!fstype)
return -EINVAL;
- type = get_fs_type(fstype);
- if (!type)
- return -ENODEV;
+ mc = vfs_fsopen(fstype);
+ if (IS_ERR(mc))
+ return PTR_ERR(mc);
+ mc->ms_flags = flags;
+ mc->mnt_flags = mnt_flags;
- mnt = vfs_kern_mount(type, flags, name, data);
- if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
- !mnt->mnt_sb->s_subtype)
- mnt = fs_set_subtype(mnt, fstype);
+ err = -ENOMEM;
+ mc->device = kstrdup(name, GFP_KERNEL);
+ if (!mc->device)
+ goto err_mc;
- put_filesystem(type);
- if (IS_ERR(mnt))
- return PTR_ERR(mnt);
+ if (mc->ops) {
+ err = parse_monolithic_mount_data(mc, data);
+ if (err < 0)
+ goto err_mc;
- if (mount_too_revealing(mnt, &mnt_flags)) {
- mntput(mnt);
- return -EPERM;
+ err = do_new_mount_mc(mc, mountpoint, mnt_flags);
+ if (err)
+ goto err_mc;
+
+ } else {
+ mnt = vfs_kern_mount(mc->fs_type, flags, name, data);
+ if (!IS_ERR(mnt) && (mc->fs_type->fs_flags & FS_HAS_SUBTYPE) &&
+ !mnt->mnt_sb->s_subtype)
+ mnt = fs_set_subtype(mnt, fstype);
+
+ if (IS_ERR(mnt)) {
+ err = PTR_ERR(mnt);
+ goto err_mc;
+ }
+
+ err = -EPERM;
+ if (mount_too_revealing(mnt, &mnt_flags))
+ goto err_mnt;
+
+ err = do_add_mount(real_mount(mnt), mountpoint, mnt_flags,
+ mc->mnt_ns);
+ if (err)
+ goto err_mnt;
}
- err = do_add_mount(real_mount(mnt), path, mnt_flags);
- if (err)
- mntput(mnt);
+ put_mount_context(mc);
+ return 0;
+
+err_mnt:
+ mntput(mnt);
+err_mc:
+ if (mc->error)
+ pr_info("Mount failed: %s\n", mc->error);
+ put_mount_context(mc);
return err;
}
@@ -2547,7 +2619,8 @@ int finish_automount(struct vfsmount *m, struct path *path)
goto fail;
}
- err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
+ err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE,
+ current->nsproxy->mnt_ns);
if (!err)
return 0;
fail:
@@ -3061,6 +3134,130 @@ SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
return ret;
}
+static struct dentry *__do_mount_mc(struct mount_context *mc)
+{
+ struct super_block *sb;
+ struct dentry *root;
+ int ret;
+
+ root = mc->ops->mount(mc);
+ if (IS_ERR(root))
+ return root;
+
+ sb = root->d_sb;
+ BUG_ON(!sb);
+ WARN_ON(!sb->s_bdi);
+ sb->s_flags |= MS_BORN;
+
+ ret = security_mount_ctx_kern_mount(mc, sb);
+ if (ret < 0)
+ goto err_sb;
+
+ /*
+ * filesystems should never set s_maxbytes larger than MAX_LFS_FILESIZE
+ * but s_maxbytes was an unsigned long long for many releases. Throw
+ * this warning for a little while to try and catch filesystems that
+ * violate this rule.
+ */
+ WARN((sb->s_maxbytes < 0), "%s set sb->s_maxbytes to "
+ "negative value (%lld)\n", mc->fs_type->name, sb->s_maxbytes);
+
+ up_write(&sb->s_umount);
+ return root;
+
+err_sb:
+ dput(root);
+ deactivate_locked_super(sb);
+ return ERR_PTR(ret);
+}
+
+struct vfsmount *vfs_kern_mount_mc(struct mount_context *mc)
+{
+ struct dentry *root;
+ struct mount *mnt;
+ int ret;
+
+ if (mc->ops->validate) {
+ ret = mc->ops->validate(mc);
+ if (ret < 0)
+ return ERR_PTR(ret);
+ }
+
+ mnt = alloc_vfsmnt(mc->device ?: "none");
+ if (!mnt)
+ return ERR_PTR(-ENOMEM);
+
+ if (mc->ms_flags & MS_KERNMOUNT)
+ mnt->mnt.mnt_flags = MNT_INTERNAL;
+
+ root = __do_mount_mc(mc);
+ if (IS_ERR(root)) {
+ mnt_free_id(mnt);
+ free_vfsmnt(mnt);
+ return ERR_CAST(root);
+ }
+
+ mnt->mnt.mnt_root = root;
+ mnt->mnt.mnt_sb = root->d_sb;
+ mnt->mnt_mountpoint = mnt->mnt.mnt_root;
+ mnt->mnt_parent = mnt;
+ lock_mount_hash();
+ list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts);
+ unlock_mount_hash();
+ return &mnt->mnt;
+}
+EXPORT_SYMBOL_GPL(vfs_kern_mount_mc);
+
+struct vfsmount *
+vfs_submount_mc(const struct dentry *mountpoint, struct mount_context *mc)
+{
+ /* Until it is worked out how to pass the user namespace
+ * through from the parent mount to the submount don't support
+ * unprivileged mounts with submounts.
+ */
+ if (mountpoint->d_sb->s_user_ns != &init_user_ns)
+ return ERR_PTR(-EPERM);
+
+ mc->ms_flags = MS_SUBMOUNT;
+ return vfs_kern_mount_mc(mc);
+}
+EXPORT_SYMBOL_GPL(vfs_submount_mc);
+
+static int do_new_mount_mc(struct mount_context *mc, struct path *mountpoint,
+ unsigned int mnt_flags)
+{
+ struct vfsmount *mnt;
+ int ret;
+
+ mnt = vfs_kern_mount_mc(mc);
+ if (IS_ERR(mnt))
+ return PTR_ERR(mnt);
+
+ if ((mc->fs_type->fs_flags & FS_HAS_SUBTYPE) &&
+ !mnt->mnt_sb->s_subtype) {
+ mnt = fs_set_subtype(mnt, mc->fs_type->name);
+ if (IS_ERR(mnt))
+ return PTR_ERR(mnt);
+ }
+
+ ret = -EPERM;
+ if (mount_too_revealing(mnt, &mnt_flags)) {
+ mc->error = "VFS: Mount too revealing";
+ goto err_mnt;
+ }
+
+ ret = do_add_mount(real_mount(mnt), mountpoint, mnt_flags, mc->mnt_ns);
+ if (ret < 0) {
+ mc->error = "VFS: Failed to add mount";
+ goto err_mnt;
+ }
+ return ret;
+
+err_mnt:
+ mntput(mnt);
+ return ret;
+}
+
/*
* Return true if path is reachable from root
*
@@ -3302,6 +3499,23 @@ struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
}
EXPORT_SYMBOL_GPL(kern_mount_data);
+struct vfsmount *kern_mount_data_mc(struct mount_context *mc)
+{
+ struct vfsmount *mnt;
+
+ mc->ms_flags = MS_KERNMOUNT;
+ mnt = vfs_kern_mount_mc(mc);
+ if (!IS_ERR(mnt)) {
+ /*
+ * it is a longterm mount, don't release mnt until
+ * we unmount before file sys is unregistered
+ */
+ real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL;
+ }
+ return mnt;
+}
+EXPORT_SYMBOL_GPL(kern_mount_data_mc);
+
void kern_unmount(struct vfsmount *mnt)
{
/* release long term mount so mount point can be released */
diff --git a/fs/super.c b/fs/super.c
index adb0c0de428c..6e7b86520337 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -805,10 +805,13 @@ struct super_block *user_get_super(dev_t dev)
* @flags: numeric part of options
* @data: the rest of options
* @force: whether or not to force the change
+ * @mc: the mount context for filesystems that support it
+ * (NULL if called from emergency or umount)
*
* Alters the mount options of a mounted file system.
*/
-int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
+int do_remount_sb(struct super_block *sb, int flags, void *data, int force,
+ struct mount_context *mc)
{
int retval;
int remount_ro;
@@ -850,8 +853,14 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
}
}
- if (sb->s_op->remount_fs) {
- retval = sb->s_op->remount_fs(sb, &flags, data);
+ if (sb->s_op->remount_fs_mc ||
+ sb->s_op->remount_fs) {
+ if (sb->s_op->remount_fs_mc) {
+ retval = sb->s_op->remount_fs_mc(sb, mc);
+ flags = mc->ms_flags;
+ } else {
+ retval = sb->s_op->remount_fs(sb, &flags, data);
+ }
if (retval) {
if (!force)
goto cancel_readonly;
@@ -898,7 +907,7 @@ static void do_emergency_remount(struct work_struct *work)
/*
* What lock protects sb->s_flags??
*/
- do_remount_sb(sb, MS_RDONLY, NULL, 1);
+ do_remount_sb(sb, MS_RDONLY, NULL, 1, NULL);
}
up_write(&sb->s_umount);
spin_lock(&sb_lock);
@@ -1048,6 +1057,37 @@ struct dentry *mount_ns(struct file_system_type *fs_type,
EXPORT_SYMBOL(mount_ns);
+struct dentry *mount_ns_mc(struct mount_context *mc, void *ns)
+{
+ struct super_block *sb;
+
+ /* Don't allow mounting unless the caller has CAP_SYS_ADMIN
+ * over the namespace.
+ */
+ if (!(mc->ms_flags & MS_KERNMOUNT) &&
+ !ns_capable(mc->user_ns, CAP_SYS_ADMIN))
+ return ERR_PTR(-EPERM);
+
+ sb = sget_userns(mc->fs_type, ns_test_super, ns_set_super,
+ mc->ms_flags, mc->user_ns, ns);
+ if (IS_ERR(sb))
+ return ERR_CAST(sb);
+
+ if (!sb->s_root) {
+ int err;
+ err = mc->ops->fill_super(sb, mc);
+ if (err) {
+ deactivate_locked_super(sb);
+ return ERR_PTR(err);
+ }
+
+ sb->s_flags |= MS_ACTIVE;
+ }
+
+ return dget(sb->s_root);
+}
+EXPORT_SYMBOL(mount_ns_mc);
+
#ifdef CONFIG_BLOCK
static int set_bdev_super(struct super_block *s, void *data)
{
@@ -1196,7 +1236,7 @@ struct dentry *mount_single(struct file_system_type *fs_type,
}
s->s_flags |= MS_ACTIVE;
} else {
- do_remount_sb(s, flags, data, 0);
+ do_remount_sb(s, flags, data, 0, NULL);
}
return dget(s->s_root);
}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 30e5c14bd743..40fe5c5054ec 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -55,6 +55,7 @@ struct workqueue_struct;
struct iov_iter;
struct fscrypt_info;
struct fscrypt_operations;
+struct mount_context;
extern void __init inode_init(void);
extern void __init inode_init_early(void);
@@ -701,6 +702,11 @@ static inline void inode_unlock(struct inode *inode)
up_write(&inode->i_rwsem);
}
+static inline int inode_lock_killable(struct inode *inode)
+{
+ return down_write_killable(&inode->i_rwsem);
+}
+
static inline void inode_lock_shared(struct inode *inode)
{
down_read(&inode->i_rwsem);
@@ -1786,6 +1792,7 @@ struct super_operations {
int (*unfreeze_fs) (struct super_block *);
int (*statfs) (struct dentry *, struct kstatfs *);
int (*remount_fs) (struct super_block *, int *, char *);
+ int (*remount_fs_mc) (struct super_block *, struct mount_context *);
void (*umount_begin) (struct super_block *);
int (*show_options)(struct seq_file *, struct dentry *);
@@ -2020,8 +2027,10 @@ struct file_system_type {
#define FS_HAS_SUBTYPE 4
#define FS_USERNS_MOUNT 8 /* Can be mounted by userns root */
#define FS_RENAME_DOES_D_MOVE 32768 /* FS will handle d_move() during rename() internally. */
+ unsigned short mc_size; /* Size of mount context to allocate */
struct dentry *(*mount) (struct file_system_type *, int,
const char *, void *);
+ int (*fsopen)(struct mount_context *, struct super_block *);
void (*kill_sb) (struct super_block *);
struct module *owner;
struct file_system_type * next;
@@ -2039,6 +2048,7 @@ struct file_system_type {
#define MODULE_ALIAS_FS(NAME) MODULE_ALIAS("fs-" NAME)
+extern struct dentry *mount_ns_mc(struct mount_context *mc, void *ns);
extern struct dentry *mount_ns(struct file_system_type *fs_type,
int flags, void *data, void *ns, struct user_namespace *user_ns,
int (*fill_super)(struct super_block *, void *, int));
@@ -2105,6 +2115,7 @@ extern int register_filesystem(struct file_system_type *);
extern int unregister_filesystem(struct file_system_type *);
extern struct vfsmount *kern_mount_data(struct file_system_type *, void *data);
#define kern_mount(type) kern_mount_data(type, NULL)
+extern struct vfsmount *kern_mount_data_mc(struct mount_context *);
extern void kern_unmount(struct vfsmount *mnt);
extern int may_umount_tree(struct vfsmount *);
extern int may_umount(struct vfsmount *);
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index e29d4c62a3c8..f6aa68b8e68e 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -75,6 +75,32 @@
* should enable secure mode.
* @bprm contains the linux_binprm structure.
*
+ * Security hooks for mount using fd context.
+ *
+ * @mount_ctx_alloc:
+ * Allocate and attach a security structure to mc->security. This pointer
+ * is initialised to NULL by the caller.
+ * @mc indicates the new mount context.
+ * @src_sb indicates the source superblock of a submount.
+ * @mount_ctx_dup:
+ * Allocate and attach a security structure to mc->security. This pointer
+ * is initialised to NULL by the caller.
+ * @mc indicates the new mount context.
+ * @src_mc indicates the original mount context.
+ * @mount_ctx_free:
+ * Clean up a mount context.
+ * @mc indicates the mount context.
+ * @mount_ctx_option:
+ * Userspace provided an option to configure a mount. The LSM may reject
+ * it with an error and may use it for itself, in which case it should
+ * return 1; otherwise it should return 0 to pass it on to the filesystem.
+ * @mc indicates the mount context.
+ * @p indicates the option in "key[=val]" form.
+ * @mount_ctx_kern_mount:
+ * Equivalent of sb_kern_mount, but with a mount_context.
+ * @mc indicates the mount context.
+ * @src_sb indicates the new superblock.
+ *
* Security hooks for filesystem operations.
*
* @sb_alloc_security:
@@ -1358,6 +1384,12 @@ union security_list_options {
void (*bprm_committing_creds)(struct linux_binprm *bprm);
void (*bprm_committed_creds)(struct linux_binprm *bprm);
+ int (*mount_ctx_alloc)(struct mount_context *mc, struct super_block *src_sb);
+ int (*mount_ctx_dup)(struct mount_context *mc, struct mount_context *src_mc);
+ void (*mount_ctx_free)(struct mount_context *mc);
+ int (*mount_ctx_option)(struct mount_context *mc, char *opt);
+ int (*mount_ctx_kern_mount)(struct mount_context *mc, struct super_block *sb);
+
int (*sb_alloc_security)(struct super_block *sb);
void (*sb_free_security)(struct super_block *sb);
int (*sb_copy_data)(char *orig, char *copy);
@@ -1666,6 +1698,11 @@ struct security_hook_heads {
struct list_head bprm_secureexec;
struct list_head bprm_committing_creds;
struct list_head bprm_committed_creds;
+ struct list_head mount_ctx_alloc;
+ struct list_head mount_ctx_dup;
+ struct list_head mount_ctx_free;
+ struct list_head mount_ctx_option;
+ struct list_head mount_ctx_kern_mount;
struct list_head sb_alloc_security;
struct list_head sb_free_security;
struct list_head sb_copy_data;
diff --git a/include/linux/mount.h b/include/linux/mount.h
index 8e0352af06b7..cf2583406986 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -69,6 +69,56 @@ struct vfsmount {
int mnt_flags;
};
+struct mount_context;
+struct mount_context_operations {
+ void (*free)(struct mount_context *mc);
+ int (*dup)(struct mount_context *mc, struct mount_context *src);
+ /* An option has been specified. */
+ int (*option)(struct mount_context *mc, char *p);
+ /* Parse monolithic mount data. */
+ int (*monolithic_mount_data)(struct mount_context *mc, void *data);
+ /* Validate the mount options */
+ int (*validate)(struct mount_context *mc);
+ /* Perform the mount. */
+ struct dentry *(*mount)(struct mount_context *mc);
+ /* Fill in a superblock */
+ int (*fill_super)(struct super_block *s, struct mount_context *mc);
+};
+
+enum mount_type {
+ MOUNT_TYPE_NEW, /* New mount made directly */
+ MOUNT_TYPE_SUBMOUNT, /* New mount made automatically */
+ MOUNT_TYPE_REMOUNT, /* Change of an existing mount */
+};
+
+/*
+ * Mount context as allocated and constructed by fsopen(). The filesystem must
+ * support the ->ctx_*() operations. The size of the object allocated is in
+ * struct file_system_type::mount_context_size; this must be embedded as the
+ * fist thing in the filesystem's own context.
+ */
+struct mount_context {
+ const struct mount_context_operations *ops;
+ struct file_system_type *fs_type;
+ struct user_namespace *user_ns; /* The user namespace for this mount */
+ struct mnt_namespace *mnt_ns; /* The mount namespace for this mount */
+ struct pid_namespace *pid_ns; /* The process ID namespace for this mount */
+ struct net *net_ns; /* The network namespace for this mount */
+ const struct cred *cred; /* The mounter's credentials */
+ char *device; /* The device name or mount target */
+ char *root_path; /* The path within the mount to mount */
+ void *security; /* The LSM context */
+ const char *error; /* Error string to be read by read() */
+ unsigned int ms_flags; /* The superblock flags (MS_*) */
+ unsigned int mnt_flags; /* The mount flags (MNT_*) */
+ bool mounted; /* Set when mounted */
+ bool sloppy; /* Unrecognised options are okay */
+ bool silent;
+ enum mount_type mount_type : 8;
+};
+
+extern const struct file_operations fs_fs_fops;
+
struct file; /* forward dec */
struct path;
@@ -90,9 +140,26 @@ struct file_system_type;
extern struct vfsmount *vfs_kern_mount(struct file_system_type *type,
int flags, const char *name,
void *data);
+extern struct vfsmount *vfs_kern_mount_mc(struct mount_context *mc);
extern struct vfsmount *vfs_submount(const struct dentry *mountpoint,
struct file_system_type *type,
const char *name, void *data);
+extern struct vfsmount *vfs_submount_mc(const struct dentry *mountpoint,
+ struct mount_context *mc);
+extern struct mount_context *vfs_fsopen(const char *fs_name);
+extern struct mount_context *__vfs_fsopen(struct file_system_type *fs_type,
+ struct super_block *src_sb,
+ unsigned int ms_flags,
+ unsigned int mnt_flags,
+ enum mount_type mount_type);
+extern struct mount_context *vfs_mntopen(struct vfsmount *mnt,
+ unsigned int ms_flags,
+ unsigned int mnt_flags,
+ enum mount_type mount_type);
+extern struct mount_context *vfs_dup_mount_context(struct mount_context *src);
+extern int vfs_mount_option(struct mount_context *mc, char *data);
+extern int generic_monolithic_mount_data(struct mount_context *ctx, void *data);
+extern void put_mount_context(struct mount_context *ctx);
extern void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list);
extern void mark_mounts_for_expiry(struct list_head *mounts);
diff --git a/include/linux/security.h b/include/linux/security.h
index 96899fad7016..91efe3039bff 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -55,6 +55,7 @@ struct msg_queue;
struct xattr;
struct xfrm_sec_ctx;
struct mm_struct;
+struct mount_context;
/* If capable should audit the security request */
#define SECURITY_CAP_NOAUDIT 0
@@ -220,6 +221,11 @@ int security_bprm_check(struct linux_binprm *bprm);
void security_bprm_committing_creds(struct linux_binprm *bprm);
void security_bprm_committed_creds(struct linux_binprm *bprm);
int security_bprm_secureexec(struct linux_binprm *bprm);
+int security_mount_ctx_alloc(struct mount_context *mc, struct super_block *sb);
+int security_mount_ctx_dup(struct mount_context *mc, struct mount_context *src);
+void security_mount_ctx_free(struct mount_context *mc);
+int security_mount_ctx_option(struct mount_context *mc, char *opt);
+int security_mount_ctx_kern_mount(struct mount_context *mc, struct super_block *sb);
int security_sb_alloc(struct super_block *sb);
void security_sb_free(struct super_block *sb);
int security_sb_copy_data(char *orig, char *copy);
@@ -513,6 +519,29 @@ static inline int security_bprm_secureexec(struct linux_binprm *bprm)
return cap_bprm_secureexec(bprm);
}
+static inline int security_mount_ctx_alloc(struct mount_context *mc,
+ struct super_block *src_sb)
+{
+ return 0;
+}
+static inline int security_mount_ctx_dup(struct mount_context *mc,
+ struct mount_context *src)
+{
+ return 0;
+}
+static inline void security_mount_ctx_free(struct mount_context *mc)
+{
+}
+static inline int security_mount_ctx_option(struct mount_context *mc, char *opt)
+{
+ return 0;
+}
+static inline int security_mount_ctx_kern_mount(struct mount_context *mc,
+ struct super_block *sb)
+{
+ return 0;
+}
+
static inline int security_sb_alloc(struct super_block *sb)
{
return 0;
diff --git a/security/security.c b/security/security.c
index 23555c5504f6..2e522361df66 100644
--- a/security/security.c
+++ b/security/security.c
@@ -309,6 +309,31 @@ int security_bprm_secureexec(struct linux_binprm *bprm)
return call_int_hook(bprm_secureexec, 0, bprm);
}
+int security_mount_ctx_alloc(struct mount_context *mc, struct super_block *src_sb)
+{
+ return call_int_hook(mount_ctx_alloc, 0, mc, src_sb);
+}
+
+int security_mount_ctx_dup(struct mount_context *mc, struct mount_context *src_mc)
+{
+ return call_int_hook(mount_ctx_dup, 0, mc, src_mc);
+}
+
+void security_mount_ctx_free(struct mount_context *mc)
+{
+ call_void_hook(mount_ctx_free, mc);
+}
+
+int security_mount_ctx_option(struct mount_context *mc, char *opt)
+{
+ return call_int_hook(mount_ctx_option, 0, mc, opt);
+}
+
+int security_mount_ctx_kern_mount(struct mount_context *mc, struct super_block *sb)
+{
+ return call_int_hook(mount_ctx_kern_mount, 0, mc, sb);
+}
+
int security_sb_alloc(struct super_block *sb)
{
return call_int_hook(sb_alloc_security, 0, sb);
@@ -1659,6 +1684,13 @@ struct security_hook_heads security_hook_heads = {
LIST_HEAD_INIT(security_hook_heads.bprm_committing_creds),
.bprm_committed_creds =
LIST_HEAD_INIT(security_hook_heads.bprm_committed_creds),
+ .mount_ctx_alloc = LIST_HEAD_INIT(security_hook_heads.mount_ctx_alloc),
+ .mount_ctx_dup = LIST_HEAD_INIT(security_hook_heads.mount_ctx_dup),
+ .mount_ctx_free = LIST_HEAD_INIT(security_hook_heads.mount_ctx_free),
+ .mount_ctx_option =
+ LIST_HEAD_INIT(security_hook_heads.mount_ctx_option),
+ .mount_ctx_kern_mount =
+ LIST_HEAD_INIT(security_hook_heads.mount_ctx_kern_mount),
.sb_alloc_security =
LIST_HEAD_INIT(security_hook_heads.sb_alloc_security),
.sb_free_security =
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 0c2ac318aa7f..cf38db840f71 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2826,6 +2826,179 @@ static int selinux_umount(struct vfsmount *mnt, int flags)
FILESYSTEM__UNMOUNT, NULL);
}
+/* fsopen mount context operations */
+
+static int selinux_mount_ctx_alloc(struct mount_context *mc,
+ struct super_block *src_sb)
+{
+ struct security_mnt_opts *opts;
+
+ opts = kzalloc(sizeof(*opts), GFP_KERNEL);
+ if (!opts)
+ return -ENOMEM;
+
+ mc->security = opts;
+ return 0;
+}
+
+static int selinux_mount_ctx_dup(struct mount_context *mc,
+ struct mount_context *src_mc)
+{
+ const struct security_mnt_opts *src = src_mc->security;
+ struct security_mnt_opts *opts;
+ int i, n;
+
+ opts = kzalloc(sizeof(*opts), GFP_KERNEL);
+ if (!opts)
+ return -ENOMEM;
+ mc->security = opts;
+
+ if (!src || !src->num_mnt_opts)
+ return 0;
+ n = opts->num_mnt_opts = src->num_mnt_opts;
+
+ if (opts->mnt_opts) {
+ opts->mnt_opts = kcalloc(n, sizeof(char *), GFP_KERNEL);
+ if (!opts->mnt_opts)
+ return -ENOMEM;
+
+ for (i = 0; i < n; i++) {
+ if (src->mnt_opts[i]) {
+ opts->mnt_opts[i] = kstrdup(src->mnt_opts[i],
+ GFP_KERNEL);
+ if (!opts->mnt_opts[i])
+ return -ENOMEM;
+ }
+ }
+ }
+
+ if (src->mnt_opts_flags) {
+ opts->mnt_opts_flags = kmemdup(src->mnt_opts_flags,
+ n * sizeof(int), GFP_KERNEL);
+ if (!opts->mnt_opts_flags)
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+static void selinux_mount_ctx_free(struct mount_context *mc)
+{
+ struct security_mnt_opts *opts = mc->security;
+
+ security_free_mnt_opts(opts);
+ mc->security = NULL;
+}
+
+static int selinux_mount_ctx_option(struct mount_context *mc, char *opt)
+{
+ struct security_mnt_opts *opts = mc->security;
+ substring_t args[MAX_OPT_ARGS];
+ unsigned int have;
+ char *c, **oo;
+ void *old;
+ int token, ctx, i;
+
+ token = match_token(opt, tokens, args);
+ if (token == Opt_error)
+ return 0; /* Doesn't belong to us. */
+
+ have = 0;
+ for (i = 0; i < opts->num_mnt_opts; i++)
+ have |= 1 << opts->mnt_opts_flags[i];
+ if (have & (1 << token)) {
+ mc->error = "SELinux: Duplicate mount options";
+ return -EINVAL;
+ }
+
+ switch (token) {
+ case Opt_context:
+ if (have & (1 << Opt_defcontext))
+ goto incompatible;
+ ctx = CONTEXT_MNT;
+ goto copy_context_string;
+
+ case Opt_fscontext:
+ ctx = FSCONTEXT_MNT;
+ goto copy_context_string;
+
+ case Opt_rootcontext:
+ ctx = ROOTCONTEXT_MNT;
+ goto copy_context_string;
+
+ case Opt_defcontext:
+ if (have & (1 << Opt_context))
+ goto incompatible;
+ ctx = DEFCONTEXT_MNT;
+ goto copy_context_string;
+
+ case Opt_labelsupport:
+ return 1;
+
+ default:
+ mc->error = "SELinux: Unknown mount option";
+ return -EINVAL;
+ }
+
+copy_context_string:
+ if (opts->num_mnt_opts > 3) {
+ mc->error = "SELinux: Too many options";
+ return -EINVAL;
+ }
+ if (!opts->mnt_opts_flags) {
+ opts->mnt_opts_flags = kcalloc(3, sizeof(int), GFP_KERNEL);
+ if (!opts->mnt_opts_flags)
+ return -ENOMEM;
+ }
+
+ if (opts->mnt_opts) {
+ oo = kmalloc((opts->num_mnt_opts + 1) * sizeof(char *),
+ GFP_KERNEL);
+ if (!oo)
+ return -ENOMEM;
+ memcpy(oo, opts->mnt_opts, opts->num_mnt_opts * sizeof(char *));
+ oo[opts->num_mnt_opts] = NULL;
+ old = opts->mnt_opts;
+ opts->mnt_opts = oo;
+ kfree(old);
+ }
+
+ c = match_strdup(&args[0]);
+ if (!c)
+ return -ENOMEM;
+ opts->mnt_opts[opts->num_mnt_opts] = c;
+ opts->mnt_opts_flags[opts->num_mnt_opts] = ctx;
+ opts->num_mnt_opts++;
+ return 1;
+
+incompatible:
+ mc->error = "SELinux: Incompatible mount options";
+ return -EINVAL;
+}
+
+static int selinux_mount_ctx_kern_mount(struct mount_context *mc,
+ struct super_block *sb)
+{
+ const struct cred *cred = current_cred();
+ struct common_audit_data ad;
+ int rc;
+
+ rc = selinux_set_mnt_opts(sb, mc->security, 0, NULL);
+ if (rc)
+ return rc;
+
+ /* Allow all mounts performed by the kernel */
+ if (mc->ms_flags & MS_KERNMOUNT)
+ return 0;
+
+ ad.type = LSM_AUDIT_DATA_DENTRY;
+ ad.u.dentry = sb->s_root;
+ rc = superblock_has_perm(cred, sb, FILESYSTEM__MOUNT, &ad);
+ if (rc < 0)
+ mc->error = "SELinux: Mount of superblock not permitted";
+ return rc;
+}
+
/* inode security operations */
static int selinux_inode_alloc_security(struct inode *inode)
@@ -6131,6 +6304,12 @@ static struct security_hook_list selinux_hooks[] = {
LSM_HOOK_INIT(bprm_committed_creds, selinux_bprm_committed_creds),
LSM_HOOK_INIT(bprm_secureexec, selinux_bprm_secureexec),
+ LSM_HOOK_INIT(mount_ctx_alloc, selinux_mount_ctx_alloc),
+ LSM_HOOK_INIT(mount_ctx_dup, selinux_mount_ctx_dup),
+ LSM_HOOK_INIT(mount_ctx_free, selinux_mount_ctx_free),
+ LSM_HOOK_INIT(mount_ctx_option, selinux_mount_ctx_option),
+ LSM_HOOK_INIT(mount_ctx_kern_mount, selinux_mount_ctx_kern_mount),
+
LSM_HOOK_INIT(sb_alloc_security, selinux_sb_alloc_security),
LSM_HOOK_INIT(sb_free_security, selinux_sb_free_security),
LSM_HOOK_INIT(sb_copy_data, selinux_sb_copy_data),