[PATCH 10/32] VFS: Implement a filesystem superblock creation/configuration context [ver #8]
From: David Howells
Date: Fri May 25 2018 - 07:58:55 EST
Implement a filesystem context concept to be used during superblock
creation for mount and superblock reconfiguration for remount.
The mounting procedure then becomes:
(1) Allocate new fs_context context.
(2) Configure the context.
(3) Create superblock.
(4) Mount the superblock any number of times.
(5) Destroy the context.
Rather than calling fs_type->mount(), an fs_context struct is created and
fs_type->init_fs_context() is called to set it up.
fs_type->fs_context_size says how much space should be allocated for the
config context. The fs_context struct is placed at the beginning and any
extra space is for the filesystem's use.
A set of operations has to be set by ->init_fs_context() to provide
freeing, duplication, option parsing, binary data parsing, validation,
mounting and superblock filling.
Legacy filesystems are supported by the provision of a set of legacy
fs_context operations that build up a list of mount options and then invoke
fs_type->mount() from within the fs_context ->get_tree() operation. This
allows all filesystems to be accessed using fs_context.
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>
---
fs/Makefile | 3
fs/fs_context.c | 599 ++++++++++++++++++++++++++++++++++++++++++++
fs/internal.h | 3
fs/libfs.c | 17 +
fs/namespace.c | 350 +++++++++++++++++---------
fs/super.c | 311 ++++++++++++++++++++++-
include/linux/fs.h | 13 +
include/linux/fs_context.h | 45 +++
include/linux/mount.h | 3
9 files changed, 1201 insertions(+), 143 deletions(-)
create mode 100644 fs/fs_context.c
diff --git a/fs/Makefile b/fs/Makefile
index c9375fd2c8c4..6f2dae3c32da 100644
--- a/fs/Makefile
+++ b/fs/Makefile
@@ -12,7 +12,8 @@ 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 d_path.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 \
+ fs_context.o
ifeq ($(CONFIG_BLOCK),y)
obj-y += buffer.o block_dev.o direct-io.o mpage.o
diff --git a/fs/fs_context.c b/fs/fs_context.c
new file mode 100644
index 000000000000..bef68a12ddb5
--- /dev/null
+++ b/fs/fs_context.c
@@ -0,0 +1,599 @@
+/* Provide a way to create a superblock configuration context within the kernel
+ * that allows a superblock to be set up prior to 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_context.h>
+#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"
+
+enum legacy_fs_param {
+ LEGACY_FS_UNSET_PARAMS,
+ LEGACY_FS_NO_PARAMS,
+ LEGACY_FS_MONOLITHIC_PARAMS,
+ LEGACY_FS_INDIVIDUAL_PARAMS,
+ LEGACY_FS_MAGIC_PARAMS,
+};
+
+struct legacy_fs_context {
+ struct fs_context fc;
+ char *legacy_data; /* Data page for legacy filesystems */
+ char *secdata;
+ size_t data_size;
+ enum legacy_fs_param param_type;
+};
+
+static const struct fs_context_operations legacy_fs_context_ops;
+
+static const match_table_t common_set_sb_flag = {
+ { SB_DIRSYNC, "dirsync" },
+ { SB_LAZYTIME, "lazytime" },
+ { SB_MANDLOCK, "mand" },
+ { SB_POSIXACL, "posixacl" },
+ { SB_RDONLY, "ro" },
+ { SB_SYNCHRONOUS, "sync" },
+ { },
+};
+
+static const match_table_t common_clear_sb_flag = {
+ { SB_LAZYTIME, "nolazytime" },
+ { SB_MANDLOCK, "nomand" },
+ { SB_RDONLY, "rw" },
+ { SB_SILENT, "silent" },
+ { SB_SYNCHRONOUS, "async" },
+ { },
+};
+
+static const match_table_t forbidden_sb_flag = {
+ { 0, "bind" },
+ { 0, "move" },
+ { 0, "private" },
+ { 0, "remount" },
+ { 0, "shared" },
+ { 0, "slave" },
+ { 0, "unbindable" },
+ { 0, "rec" },
+ { 0, "noatime" },
+ { 0, "relatime" },
+ { 0, "norelatime" },
+ { 0, "strictatime" },
+ { 0, "nostrictatime" },
+ { 0, "nodiratime" },
+ { 0, "dev" },
+ { 0, "nodev" },
+ { 0, "exec" },
+ { 0, "noexec" },
+ { 0, "suid" },
+ { 0, "nosuid" },
+ { },
+};
+
+/*
+ * Check for a common mount option that manipulates s_flags.
+ */
+static int vfs_parse_sb_flag_option(struct fs_context *fc, char *data)
+{
+ substring_t args[MAX_OPT_ARGS];
+ unsigned int token;
+
+ token = match_token(data, common_set_sb_flag, args);
+ if (token) {
+ fc->sb_flags |= token;
+ return 1;
+ }
+
+ token = match_token(data, common_clear_sb_flag, args);
+ if (token) {
+ fc->sb_flags &= ~token;
+ return 1;
+ }
+
+ token = match_token(data, forbidden_sb_flag, args);
+ if (token)
+ return -EINVAL;
+
+ return 0;
+}
+
+/**
+ * vfs_parse_fs_option - Add a single mount option to a superblock config
+ * @fc: The filesystem context to modify
+ * @opt: The option to apply.
+ * @len: The length of the option.
+ *
+ * A single mount option in string form is applied to the filesystem context
+ * being set up. Certain standard options (for example "ro") are translated
+ * into flag bits without going to the filesystem. The active security module
+ * is 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, supplementary error information may have been set.
+ */
+int vfs_parse_fs_option(struct fs_context *fc, char *opt, size_t len)
+{
+ int ret;
+
+ ret = vfs_parse_sb_flag_option(fc, opt);
+ if (ret < 0)
+ return ret;
+ if (ret == 1)
+ return 0;
+
+ ret = security_fs_context_parse_option(fc, opt, len);
+ if (ret < 0)
+ return ret;
+ if (ret == 1)
+ return 0;
+
+ if (fc->ops->parse_option)
+ return fc->ops->parse_option(fc, opt, len);
+
+ return -EINVAL;
+}
+EXPORT_SYMBOL(vfs_parse_fs_option);
+
+/**
+ * vfs_set_fs_source - Set the source/device name in a filesystem context
+ * @fc: The filesystem context to alter
+ * @source: The name of the source
+ * @slen: Length of @source string
+ */
+int vfs_set_fs_source(struct fs_context *fc, const char *source, size_t slen)
+{
+ char *src;
+ int ret;
+
+ if (fc->source)
+ return -EINVAL;
+ src = kmemdup_nul(source, slen, GFP_KERNEL);
+ if (!src)
+ return -ENOMEM;
+
+ ret = security_fs_context_parse_source(fc, src);
+ if (ret < 0)
+ goto error;
+
+ if (fc->ops->parse_source) {
+ ret = fc->ops->parse_source(fc, src);
+ if (ret < 0)
+ goto error;
+ }
+
+ fc->source = src;
+ return 0;
+
+error:
+ kfree(src);
+ return ret;
+}
+EXPORT_SYMBOL(vfs_set_fs_source);
+
+/**
+ * generic_parse_monolithic - Parse key[=val][,key[=val]]* mount data
+ * @ctx: The superblock configuration to fill in.
+ * @data: The data to parse
+ * @data_size: The amount of data
+ *
+ * Parse a blob of data that's in key[=val][,key[=val]]* form. This can be
+ * called from the ->monolithic_mount_data() fs_context operation.
+ *
+ * Returns 0 on success or the error returned by the ->parse_option() fs_context
+ * operation on failure.
+ */
+int generic_parse_monolithic(struct fs_context *fc, void *data, size_t data_size)
+{
+ char *options = data, *opt;
+ int ret;
+
+ if (!options)
+ return 0;
+
+ while ((opt = strsep(&options, ",")) != NULL) {
+ if (*opt) {
+ ret = vfs_parse_fs_option(fc, opt, strlen(opt));
+ if (ret < 0)
+ return ret;
+ }
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(generic_parse_monolithic);
+
+/**
+ * vfs_new_fs_context - Create a filesystem context.
+ * @fs_type: The filesystem type.
+ * @reference: The dentry from which this one derives (or NULL)
+ * @sb_flags: Filesystem/superblock flags (SB_*)
+ * @purpose: The purpose that this configuration shall be used for.
+ *
+ * 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 (referred to by @reference) is supplied, may have
+ * parameters such as namespaces copied across from that superblock.
+ */
+struct fs_context *vfs_new_fs_context(struct file_system_type *fs_type,
+ struct dentry *reference,
+ unsigned int sb_flags,
+ enum fs_context_purpose purpose)
+{
+ struct fs_context *fc;
+ int ret;
+
+ fc = kzalloc(sizeof(struct legacy_fs_context), GFP_KERNEL);
+ if (!fc)
+ return ERR_PTR(-ENOMEM);
+
+ fc->purpose = purpose;
+ fc->sb_flags = sb_flags;
+ fc->fs_type = get_filesystem(fs_type);
+ fc->cred = get_current_cred();
+
+ switch (purpose) {
+ case FS_CONTEXT_FOR_KERNEL_MOUNT:
+ fc->sb_flags |= SB_KERNMOUNT;
+ /* Fallthrough */
+ case FS_CONTEXT_FOR_USER_MOUNT:
+ fc->user_ns = get_user_ns(fc->cred->user_ns);
+ fc->net_ns = get_net(current->nsproxy->net_ns);
+ break;
+ case FS_CONTEXT_FOR_SUBMOUNT:
+ fc->user_ns = get_user_ns(reference->d_sb->s_user_ns);
+ fc->net_ns = get_net(current->nsproxy->net_ns);
+ break;
+ case FS_CONTEXT_FOR_RECONFIGURE:
+ /* We don't pin any namespaces as the superblock's
+ * subscriptions cannot be changed at this point.
+ */
+ fc->root = dget(reference);
+ break;
+ }
+
+
+ /* TODO: Make all filesystems support this unconditionally */
+ if (fc->fs_type->init_fs_context) {
+ ret = fc->fs_type->init_fs_context(fc, reference);
+ if (ret < 0)
+ goto err_fc;
+ } else {
+ fc->ops = &legacy_fs_context_ops;
+ }
+
+ /* Do the security check last because ->init_fs_context may change the
+ * namespace subscriptions.
+ */
+ ret = security_fs_context_alloc(fc, reference);
+ if (ret < 0)
+ goto err_fc;
+
+ return fc;
+
+err_fc:
+ put_fs_context(fc);
+ return ERR_PTR(ret);
+}
+EXPORT_SYMBOL(vfs_new_fs_context);
+
+/**
+ * vfs_sb_reconfig - Create a filesystem context for remount/reconfiguration
+ * @mountpoint: The mountpoint to open
+ * @sb_flags: Filesystem/superblock flags (SB_*)
+ *
+ * Open a mounted filesystem and create a filesystem context such that a
+ * remount can be effected.
+ */
+struct fs_context *vfs_sb_reconfig(struct path *mountpoint,
+ unsigned int sb_flags)
+{
+ struct fs_context *fc;
+
+ fc = vfs_new_fs_context(mountpoint->dentry->d_sb->s_type,
+ mountpoint->dentry,
+ sb_flags, FS_CONTEXT_FOR_RECONFIGURE);
+ if (IS_ERR(fc))
+ return fc;
+
+ return fc;
+}
+
+/**
+ * vfs_dup_fc_config: Duplicate a filesytem context.
+ * @src_fc: The context to copy.
+ */
+struct fs_context *vfs_dup_fs_context(struct fs_context *src_fc)
+{
+ struct fs_context *fc;
+ int ret;
+
+ if (!src_fc->ops->dup)
+ return ERR_PTR(-ENOTSUPP);
+
+ fc = kmemdup(src_fc, sizeof(struct legacy_fs_context), GFP_KERNEL);
+ if (!fc)
+ return ERR_PTR(-ENOMEM);
+
+ fc->fs_private = NULL;
+ fc->source = NULL;
+ fc->security = NULL;
+ get_filesystem(fc->fs_type);
+ get_net(fc->net_ns);
+ get_user_ns(fc->user_ns);
+ get_cred(fc->cred);
+
+ /* Can't call put until we've called ->dup */
+ ret = fc->ops->dup(fc, src_fc);
+ if (ret < 0)
+ goto err_fc;
+
+ ret = security_fs_context_dup(fc, src_fc);
+ if (ret < 0)
+ goto err_fc;
+ return fc;
+
+err_fc:
+ put_fs_context(fc);
+ return ERR_PTR(ret);
+}
+EXPORT_SYMBOL(vfs_dup_fs_context);
+
+/**
+ * put_fs_context - Dispose of a superblock configuration context.
+ * @fc: The context to dispose of.
+ */
+void put_fs_context(struct fs_context *fc)
+{
+ struct super_block *sb;
+
+ if (fc->root) {
+ sb = fc->root->d_sb;
+ dput(fc->root);
+ fc->root = NULL;
+ if (fc->drop_sb) {
+ deactivate_super(sb);
+ fc->drop_sb = false;
+ }
+ }
+
+ if (fc->ops && fc->ops->free)
+ fc->ops->free(fc);
+
+ security_fs_context_free(fc);
+ if (fc->net_ns)
+ put_net(fc->net_ns);
+ put_user_ns(fc->user_ns);
+ if (fc->cred)
+ put_cred(fc->cred);
+ kfree(fc->subtype);
+ put_filesystem(fc->fs_type);
+ kfree(fc->source);
+ kfree(fc);
+}
+EXPORT_SYMBOL(put_fs_context);
+
+/*
+ * Free the config for a filesystem that doesn't support fs_context.
+ */
+static void legacy_fs_context_free(struct fs_context *fc)
+{
+ struct legacy_fs_context *ctx = container_of(fc, struct legacy_fs_context, fc);
+
+ free_secdata(ctx->secdata);
+ switch (ctx->param_type) {
+ case LEGACY_FS_UNSET_PARAMS:
+ case LEGACY_FS_NO_PARAMS:
+ break;
+ case LEGACY_FS_MAGIC_PARAMS:
+ break; /* ctx->data is a weird pointer */
+ default:
+ kfree(ctx->legacy_data);
+ break;
+ }
+}
+
+/*
+ * Duplicate a legacy config.
+ */
+static int legacy_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc)
+{
+ struct legacy_fs_context *ctx = container_of(fc, struct legacy_fs_context, fc);
+ struct legacy_fs_context *src_ctx = container_of(src_fc, struct legacy_fs_context, fc);
+
+ switch (ctx->param_type) {
+ case LEGACY_FS_MONOLITHIC_PARAMS:
+ case LEGACY_FS_INDIVIDUAL_PARAMS:
+ ctx->legacy_data = kmemdup(src_ctx->legacy_data,
+ src_ctx->data_size, GFP_KERNEL);
+ if (!ctx->legacy_data)
+ return -ENOMEM;
+ /* Fall through */
+ default:
+ break;
+ }
+ return 0;
+}
+
+/*
+ * Add an option to a legacy config. We build up a comma-separated list of
+ * options.
+ */
+static int legacy_parse_option(struct fs_context *fc, char *opt, size_t len)
+{
+ struct legacy_fs_context *ctx = container_of(fc, struct legacy_fs_context, fc);
+ unsigned int size = ctx->data_size;
+
+ if (ctx->param_type != LEGACY_FS_UNSET_PARAMS &&
+ ctx->param_type != LEGACY_FS_INDIVIDUAL_PARAMS) {
+ pr_warn("VFS: Can't mix monolithic and individual options\n");
+ return -EINVAL;
+ }
+
+ if (len > PAGE_SIZE - 2 - size)
+ return -EINVAL;
+ if (memchr(opt, ',', len) != NULL)
+ return -EINVAL;
+ if (!ctx->legacy_data) {
+ ctx->legacy_data = kmalloc(PAGE_SIZE, GFP_KERNEL);
+ if (!ctx->legacy_data)
+ return -ENOMEM;
+ }
+
+ ctx->legacy_data[size++] = ',';
+ memcpy(ctx->legacy_data + size, opt, len);
+ size += len;
+ ctx->legacy_data[size] = '\0';
+ ctx->data_size = size;
+ ctx->param_type = LEGACY_FS_INDIVIDUAL_PARAMS;
+ return 0;
+}
+
+/*
+ * Add monolithic mount data.
+ */
+static int legacy_parse_monolithic(struct fs_context *fc, void *data, size_t data_size)
+{
+ struct legacy_fs_context *ctx = container_of(fc, struct legacy_fs_context, fc);
+
+ if (ctx->param_type != LEGACY_FS_UNSET_PARAMS) {
+ pr_warn("VFS: Can't mix monolithic and individual options\n");
+ return -EINVAL;
+ }
+
+ if (!data) {
+ ctx->param_type = LEGACY_FS_NO_PARAMS;
+ return 0;
+ }
+
+ ctx->data_size = data_size;
+ if (data_size > 0) {
+ ctx->legacy_data = kmemdup(data, data_size, GFP_KERNEL);
+ if (!ctx->legacy_data)
+ return -ENOMEM;
+ ctx->param_type = LEGACY_FS_MONOLITHIC_PARAMS;
+ } else {
+ /* Some filesystems pass weird pointers through that we don't
+ * want to copy. They can indicate this by setting data_size
+ * to 0.
+ */
+ ctx->legacy_data = data;
+ ctx->param_type = LEGACY_FS_MAGIC_PARAMS;
+ }
+
+ return 0;
+}
+
+/*
+ * Use the legacy mount validation step to strip out and process security
+ * config options.
+ */
+static int legacy_validate(struct fs_context *fc)
+{
+ struct legacy_fs_context *ctx = container_of(fc, struct legacy_fs_context, fc);
+
+ switch (ctx->param_type) {
+ case LEGACY_FS_UNSET_PARAMS:
+ ctx->param_type = LEGACY_FS_NO_PARAMS;
+ /* Fall through */
+ case LEGACY_FS_NO_PARAMS:
+ case LEGACY_FS_MAGIC_PARAMS:
+ return 0;
+ default:
+ break;
+ }
+
+ if (ctx->fc.fs_type->fs_flags & FS_BINARY_MOUNTDATA)
+ return 0;
+
+ ctx->secdata = alloc_secdata();
+ if (!ctx->secdata)
+ return -ENOMEM;
+
+ return security_sb_copy_data(ctx->legacy_data, ctx->data_size,
+ ctx->secdata);
+}
+
+/*
+ * Determine the superblock subtype.
+ */
+static int legacy_set_subtype(struct fs_context *fc)
+{
+ const char *subtype = strchr(fc->fs_type->name, '.');
+
+ if (subtype) {
+ subtype++;
+ if (!subtype[0])
+ return -EINVAL;
+ } else {
+ subtype = "";
+ }
+
+ fc->subtype = kstrdup(subtype, GFP_KERNEL);
+ if (!fc->subtype)
+ return -ENOMEM;
+ return 0;
+}
+
+/*
+ * Get a mountable root with the legacy mount command.
+ */
+static int legacy_get_tree(struct fs_context *fc)
+{
+ struct legacy_fs_context *ctx = container_of(fc, struct legacy_fs_context, fc);
+ struct super_block *sb;
+ struct dentry *root;
+ int ret;
+
+ root = ctx->fc.fs_type->mount(ctx->fc.fs_type, ctx->fc.sb_flags,
+ ctx->fc.source, ctx->legacy_data,
+ ctx->data_size);
+ if (IS_ERR(root))
+ return PTR_ERR(root);
+
+ sb = root->d_sb;
+ BUG_ON(!sb);
+
+ if ((ctx->fc.fs_type->fs_flags & FS_HAS_SUBTYPE) &&
+ !fc->subtype) {
+ ret = legacy_set_subtype(fc);
+ if (ret < 0)
+ goto err_sb;
+ }
+
+ ctx->fc.root = root;
+ ctx->fc.drop_sb = true;
+ return 0;
+
+err_sb:
+ dput(root);
+ deactivate_locked_super(sb);
+ return ret;
+}
+
+static const struct fs_context_operations legacy_fs_context_ops = {
+ .free = legacy_fs_context_free,
+ .dup = legacy_fs_context_dup,
+ .parse_option = legacy_parse_option,
+ .parse_monolithic = legacy_parse_monolithic,
+ .validate = legacy_validate,
+ .get_tree = legacy_get_tree,
+};
diff --git a/fs/internal.h b/fs/internal.h
index 1afa522c5f30..91a990234488 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -98,7 +98,8 @@ extern struct file *get_empty_filp(void);
/*
* super.c
*/
-extern int do_remount_sb(struct super_block *, int, void *, size_t, int);
+extern int do_remount_sb(struct super_block *, int, void *, size_t, int,
+ struct fs_context *);
extern bool trylock_super(struct super_block *sb);
extern struct dentry *mount_fs(struct file_system_type *,
int, const char *, void *, size_t);
diff --git a/fs/libfs.c b/fs/libfs.c
index 9f1f4884b7cc..823f0510e43d 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -9,6 +9,7 @@
#include <linux/slab.h>
#include <linux/cred.h>
#include <linux/mount.h>
+#include <linux/fs_context.h>
#include <linux/vfs.h>
#include <linux/quotaops.h>
#include <linux/mutex.h>
@@ -574,13 +575,27 @@ static DEFINE_SPINLOCK(pin_fs_lock);
int simple_pin_fs(struct file_system_type *type, struct vfsmount **mount, int *count)
{
+ struct fs_context *fc;
struct vfsmount *mnt = NULL;
+ int ret;
+
spin_lock(&pin_fs_lock);
if (unlikely(!*mount)) {
spin_unlock(&pin_fs_lock);
- mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL, 0);
+
+ fc = vfs_new_fs_context(type, NULL, 0, FS_CONTEXT_FOR_KERNEL_MOUNT);
+ if (IS_ERR(fc))
+ return PTR_ERR(fc);
+
+ ret = vfs_get_tree(fc);
+ if (ret < 0)
+ return ret;
+
+ mnt = vfs_create_mount(fc, 0);
+ put_fs_context(fc);
if (IS_ERR(mnt))
return PTR_ERR(mnt);
+
spin_lock(&pin_fs_lock);
if (!*mount)
*mount = mnt;
diff --git a/fs/namespace.c b/fs/namespace.c
index a6ab1137f8d2..14be35d02050 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -25,8 +25,10 @@
#include <linux/magic.h>
#include <linux/bootmem.h>
#include <linux/task_work.h>
+#include <linux/file.h>
#include <linux/sched/task.h>
#include <uapi/linux/mount.h>
+#include <linux/fs_context.h>
#include "pnode.h"
#include "internal.h"
@@ -1019,56 +1021,6 @@ static struct mount *skip_mnt_tree(struct mount *p)
return p;
}
-struct vfsmount *
-vfs_kern_mount(struct file_system_type *type, int flags, const char *name,
- void *data, size_t data_size)
-{
- struct mount *mnt;
- struct dentry *root;
-
- if (!type)
- return ERR_PTR(-ENODEV);
-
- mnt = alloc_vfsmnt(name);
- if (!mnt)
- return ERR_PTR(-ENOMEM);
-
- if (flags & SB_KERNMOUNT)
- mnt->mnt.mnt_flags = MNT_INTERNAL;
-
- root = mount_fs(type, flags, name, data, data_size);
- 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);
-
-struct vfsmount *
-vfs_submount(const struct dentry *mountpoint, struct file_system_type *type,
- const char *name, void *data, size_t data_size)
-{
- /* 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);
-
- return vfs_kern_mount(type, SB_SUBMOUNT, name, data, data_size);
-}
-EXPORT_SYMBOL_GPL(vfs_submount);
-
static struct mount *clone_mnt(struct mount *old, struct dentry *root,
int flag)
{
@@ -1596,7 +1548,7 @@ static int do_umount(struct mount *mnt, int flags)
return -EPERM;
down_write(&sb->s_umount);
if (!sb_rdonly(sb))
- retval = do_remount_sb(sb, SB_RDONLY, NULL, 0, 0);
+ retval = do_remount_sb(sb, SB_RDONLY, NULL, 0, 0, NULL);
up_write(&sb->s_umount);
return retval;
}
@@ -2283,6 +2235,20 @@ static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
return error;
}
+/*
+ * Parse the monolithic page of mount data given to sys_mount().
+ */
+static int parse_monolithic_mount_data(struct fs_context *fc, void *data, size_t data_size)
+{
+ int (*monolithic_mount_data)(struct fs_context *, void *, size_t);
+
+ monolithic_mount_data = fc->ops->parse_monolithic;
+ if (!monolithic_mount_data)
+ monolithic_mount_data = generic_parse_monolithic;
+
+ return monolithic_mount_data(fc, data, data_size);
+}
+
/*
* 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
@@ -2291,9 +2257,11 @@ static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
static int do_remount(struct path *path, int ms_flags, int sb_flags,
int mnt_flags, void *data, size_t data_size)
{
+ struct fs_context *fc = 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;
@@ -2328,9 +2296,29 @@ static int do_remount(struct path *path, int ms_flags, int sb_flags,
return -EPERM;
}
- err = security_sb_remount(sb, data, data_size);
- if (err)
- return err;
+ if (type->init_fs_context) {
+ fc = vfs_sb_reconfig(path, sb_flags);
+ if (IS_ERR(fc))
+ return PTR_ERR(fc);
+
+ err = parse_monolithic_mount_data(fc, data, data_size);
+ if (err < 0)
+ goto err_fc;
+
+ if (fc->ops->validate) {
+ err = fc->ops->validate(fc);
+ if (err < 0)
+ goto err_fc;
+ }
+
+ err = security_fs_context_validate(fc);
+ if (err)
+ return err;
+ } else {
+ err = security_sb_remount(sb, data, data_size);
+ if (err)
+ return err;
+ }
down_write(&sb->s_umount);
if (ms_flags & MS_BIND)
@@ -2338,7 +2326,7 @@ static int do_remount(struct path *path, int ms_flags, int sb_flags,
else if (!capable(CAP_SYS_ADMIN))
err = -EPERM;
else
- err = do_remount_sb(sb, sb_flags, data, data_size, 0);
+ err = do_remount_sb(sb, sb_flags, data, data_size, 0, fc);
if (!err) {
lock_mount_hash();
mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK;
@@ -2347,6 +2335,9 @@ static int do_remount(struct path *path, int ms_flags, int sb_flags,
unlock_mount_hash();
}
up_write(&sb->s_umount);
+err_fc:
+ if (fc)
+ put_fs_context(fc);
return err;
}
@@ -2430,29 +2421,6 @@ static int do_move_mount(struct path *path, const char *old_name)
return err;
}
-static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
-{
- int err;
- const char *subtype = strchr(fstype, '.');
- if (subtype) {
- subtype++;
- err = -EINVAL;
- if (!subtype[0])
- goto err;
- } else
- subtype = "";
-
- mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
- err = -ENOMEM;
- if (!mnt->mnt_sb->s_subtype)
- goto err;
- return mnt;
-
- err:
- mntput(mnt);
- return ERR_PTR(err);
-}
-
/*
* add a mount into a namespace's mount tree
*/
@@ -2497,44 +2465,88 @@ static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags)
return err;
}
-static bool mount_too_revealing(struct vfsmount *mnt, int *new_mnt_flags);
+static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags);
+
+/*
+ * Create a new mount using a superblock configuration and request it
+ * be added to the namespace tree.
+ */
+static int do_new_mount_fc(struct fs_context *fc, struct path *mountpoint,
+ unsigned int mnt_flags)
+{
+ struct vfsmount *mnt;
+ int ret;
+
+ ret = security_sb_mountpoint(fc, mountpoint,
+ mnt_flags & ~MNT_INTERNAL_FLAGS);
+ if (ret < 0)
+ return ret;
+
+ if (mount_too_revealing(fc->root->d_sb, &mnt_flags)) {
+ pr_warn("VFS: Mount too revealing\n");
+ return -EPERM;
+ }
+
+ mnt = vfs_create_mount(fc, mnt_flags);
+ if (IS_ERR(mnt))
+ return PTR_ERR(mnt);
+
+ ret = do_add_mount(real_mount(mnt), mountpoint, mnt_flags);
+ if (ret < 0)
+ goto err_mnt;
+ return ret;
+
+err_mnt:
+ mntput(mnt);
+ return ret;
+}
/*
* 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 sb_flags,
- int mnt_flags, const char *name,
+static int do_new_mount(struct path *mountpoint, const char *fstype,
+ int sb_flags, int mnt_flags, const char *name,
void *data, size_t data_size)
{
- struct file_system_type *type;
- struct vfsmount *mnt;
+ struct file_system_type *fs_type;
+ struct fs_context *fc;
int err;
if (!fstype)
return -EINVAL;
- type = get_fs_type(fstype);
- if (!type)
- return -ENODEV;
-
- mnt = vfs_kern_mount(type, sb_flags, name, data, data_size);
- if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
- !mnt->mnt_sb->s_subtype)
- mnt = fs_set_subtype(mnt, fstype);
+ err = -ENODEV;
+ fs_type = get_fs_type(fstype);
+ if (!fs_type)
+ goto out;
- put_filesystem(type);
- if (IS_ERR(mnt))
- return PTR_ERR(mnt);
+ fc = vfs_new_fs_context(fs_type, NULL, sb_flags,
+ FS_CONTEXT_FOR_USER_MOUNT);
+ put_filesystem(fs_type);
+ if (IS_ERR(fc)) {
+ err = PTR_ERR(fc);
+ goto out;
+ }
- if (mount_too_revealing(mnt, &mnt_flags)) {
- mntput(mnt);
- return -EPERM;
+ if (name) {
+ err = vfs_set_fs_source(fc, name, strlen(name));
+ if (err < 0)
+ goto out_fc;
}
- err = do_add_mount(real_mount(mnt), path, mnt_flags);
- if (err)
- mntput(mnt);
+ err = parse_monolithic_mount_data(fc, data, data_size);
+ if (err < 0)
+ goto out_fc;
+
+ err = vfs_get_tree(fc);
+ if (err < 0)
+ goto out_fc;
+
+ err = do_new_mount_fc(fc, mountpoint, mnt_flags);
+out_fc:
+ put_fs_context(fc);
+out:
return err;
}
@@ -3082,6 +3094,117 @@ SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
return ksys_mount(dev_name, dir_name, type, flags, data);
}
+/**
+ * vfs_create_mount - Create a mount for a configured superblock
+ * @fc: The configuration context with the superblock attached
+ * @mnt_flags: The mount flags to apply
+ *
+ * Create a mount to an already configured superblock. If necessary, the
+ * caller should invoke vfs_get_tree() before calling this.
+ *
+ * Note that this does not attach the mount to anything.
+ */
+struct vfsmount *vfs_create_mount(struct fs_context *fc, unsigned int mnt_flags)
+{
+ struct mount *mnt;
+
+ if (!fc->root)
+ return ERR_PTR(-EINVAL);
+
+ mnt = alloc_vfsmnt(fc->source ?: "none");
+ if (!mnt)
+ return ERR_PTR(-ENOMEM);
+
+ if (fc->purpose == FS_CONTEXT_FOR_KERNEL_MOUNT)
+ /* It's a longterm mount, don't release mnt until we unmount
+ * before file sys is unregistered
+ */
+ mnt_flags |= MNT_INTERNAL;
+
+ atomic_inc(&fc->root->d_sb->s_active);
+ mnt->mnt.mnt_flags = mnt_flags;
+ mnt->mnt.mnt_sb = fc->root->d_sb;
+ mnt->mnt.mnt_root = dget(fc->root);
+ mnt->mnt_mountpoint = mnt->mnt.mnt_root;
+ mnt->mnt_parent = mnt;
+
+ lock_mount_hash();
+ list_add_tail(&mnt->mnt_instance, &mnt->mnt.mnt_sb->s_mounts);
+ unlock_mount_hash();
+ return &mnt->mnt;
+}
+EXPORT_SYMBOL(vfs_create_mount);
+
+struct vfsmount *vfs_kern_mount(struct file_system_type *type,
+ int sb_flags, const char *devname,
+ void *data, size_t data_size)
+{
+ struct fs_context *fc;
+ struct vfsmount *mnt;
+ int ret;
+
+ if (!type)
+ return ERR_PTR(-EINVAL);
+
+ fc = vfs_new_fs_context(type, NULL, sb_flags,
+ sb_flags & SB_KERNMOUNT ?
+ FS_CONTEXT_FOR_KERNEL_MOUNT :
+ FS_CONTEXT_FOR_USER_MOUNT);
+ if (IS_ERR(fc))
+ return ERR_CAST(fc);
+
+ if (devname) {
+ ret = vfs_set_fs_source(fc, devname, strlen(devname));
+ if (ret < 0)
+ goto err_fc;
+ }
+
+ ret = parse_monolithic_mount_data(fc, data, data_size);
+ if (ret < 0)
+ goto err_fc;
+
+ ret = vfs_get_tree(fc);
+ if (ret < 0)
+ goto err_fc;
+
+ mnt = vfs_create_mount(fc, 0);
+out:
+ put_fs_context(fc);
+ return mnt;
+err_fc:
+ mnt = ERR_PTR(ret);
+ goto out;
+}
+EXPORT_SYMBOL_GPL(vfs_kern_mount);
+
+struct vfsmount *
+vfs_submount(const struct dentry *mountpoint, struct file_system_type *type,
+ const char *name, void *data, size_t data_size)
+{
+ /* 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);
+
+ return vfs_kern_mount(type, MS_SUBMOUNT, name, data, data_size);
+}
+EXPORT_SYMBOL_GPL(vfs_submount);
+
+struct vfsmount *kern_mount(struct file_system_type *type)
+{
+ return vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL, 0);
+}
+EXPORT_SYMBOL_GPL(kern_mount);
+
+struct vfsmount *kern_mount_data(struct file_system_type *type,
+ void *data, size_t data_size)
+{
+ return vfs_kern_mount(type, SB_KERNMOUNT, type->name, data, data_size);
+}
+EXPORT_SYMBOL_GPL(kern_mount_data);
+
/*
* Return true if path is reachable from root
*
@@ -3302,22 +3425,6 @@ void put_mnt_ns(struct mnt_namespace *ns)
free_mnt_ns(ns);
}
-struct vfsmount *kern_mount_data(struct file_system_type *type,
- void *data, size_t data_size)
-{
- struct vfsmount *mnt;
- mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, data, data_size);
- 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);
-
void kern_unmount(struct vfsmount *mnt)
{
/* release long term mount so mount point can be released */
@@ -3358,7 +3465,8 @@ bool current_chrooted(void)
return chrooted;
}
-static bool mnt_already_visible(struct mnt_namespace *ns, struct vfsmount *new,
+static bool mnt_already_visible(struct mnt_namespace *ns,
+ const struct super_block *sb,
int *new_mnt_flags)
{
int new_flags = *new_mnt_flags;
@@ -3370,7 +3478,7 @@ static bool mnt_already_visible(struct mnt_namespace *ns, struct vfsmount *new,
struct mount *child;
int mnt_flags;
- if (mnt->mnt.mnt_sb->s_type != new->mnt_sb->s_type)
+ if (mnt->mnt.mnt_sb->s_type != sb->s_type)
continue;
/* This mount is not fully visible if it's root directory
@@ -3421,7 +3529,7 @@ static bool mnt_already_visible(struct mnt_namespace *ns, struct vfsmount *new,
return visible;
}
-static bool mount_too_revealing(struct vfsmount *mnt, int *new_mnt_flags)
+static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags)
{
const unsigned long required_iflags = SB_I_NOEXEC | SB_I_NODEV;
struct mnt_namespace *ns = current->nsproxy->mnt_ns;
@@ -3431,7 +3539,7 @@ static bool mount_too_revealing(struct vfsmount *mnt, int *new_mnt_flags)
return false;
/* Can this filesystem be too revealing? */
- s_iflags = mnt->mnt_sb->s_iflags;
+ s_iflags = sb->s_iflags;
if (!(s_iflags & SB_I_USERNS_VISIBLE))
return false;
@@ -3441,7 +3549,7 @@ static bool mount_too_revealing(struct vfsmount *mnt, int *new_mnt_flags)
return true;
}
- return !mnt_already_visible(ns, mnt, new_mnt_flags);
+ return !mnt_already_visible(ns, sb, new_mnt_flags);
}
bool mnt_may_suid(struct vfsmount *mnt)
diff --git a/fs/super.c b/fs/super.c
index c9d208b7999e..b9d386d728c6 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -36,6 +36,7 @@
#include <linux/lockdep.h>
#include <linux/user_namespace.h>
#include <uapi/linux/mount.h>
+#include <linux/fs_context.h>
#include "internal.h"
static int thaw_super_locked(struct super_block *sb);
@@ -184,16 +185,13 @@ static void destroy_unused_super(struct super_block *s)
}
/**
- * alloc_super - create new superblock
- * @type: filesystem type superblock should belong to
- * @flags: the mount flags
- * @user_ns: User namespace for the super_block
+ * alloc_super - Create new superblock
+ * @fc: The filesystem configuration context
*
* Allocates and initializes a new &struct super_block. alloc_super()
* returns a pointer new superblock or %NULL if allocation had failed.
*/
-static struct super_block *alloc_super(struct file_system_type *type, int flags,
- struct user_namespace *user_ns)
+static struct super_block *alloc_super(struct fs_context *fc)
{
struct super_block *s = kzalloc(sizeof(struct super_block), GFP_USER);
static const struct super_operations default_op;
@@ -203,9 +201,9 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags,
return NULL;
INIT_LIST_HEAD(&s->s_mounts);
- s->s_user_ns = get_user_ns(user_ns);
+ s->s_user_ns = get_user_ns(fc->user_ns);
init_rwsem(&s->s_umount);
- lockdep_set_class(&s->s_umount, &type->s_umount_key);
+ lockdep_set_class(&s->s_umount, &fc->fs_type->s_umount_key);
/*
* sget() can have s_umount recursion.
*
@@ -229,12 +227,12 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags,
for (i = 0; i < SB_FREEZE_LEVELS; i++) {
if (__percpu_init_rwsem(&s->s_writers.rw_sem[i],
sb_writers_name[i],
- &type->s_writers_key[i]))
+ &fc->fs_type->s_writers_key[i]))
goto fail;
}
init_waitqueue_head(&s->s_writers.wait_unfrozen);
s->s_bdi = &noop_backing_dev_info;
- s->s_flags = flags;
+ s->s_flags = fc->sb_flags;
if (s->s_user_ns != &init_user_ns)
s->s_iflags |= SB_I_NODEV;
INIT_HLIST_NODE(&s->s_instances);
@@ -252,7 +250,7 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags,
s->s_count = 1;
atomic_set(&s->s_active, 1);
mutex_init(&s->s_vfs_rename_mutex);
- lockdep_set_class(&s->s_vfs_rename_mutex, &type->s_vfs_rename_key);
+ lockdep_set_class(&s->s_vfs_rename_mutex, &fc->fs_type->s_vfs_rename_key);
init_rwsem(&s->s_dquot.dqio_sem);
s->s_maxbytes = MAX_NON_LFS;
s->s_op = &default_op;
@@ -472,6 +470,97 @@ void generic_shutdown_super(struct super_block *sb)
EXPORT_SYMBOL(generic_shutdown_super);
+/**
+ * sget_fc - Find or create a superblock
+ * @fc: Filesystem context.
+ * @test: Comparison callback
+ * @set: Setup callback
+ *
+ * Find or create a superblock using the parameters stored in the filesystem
+ * context and the two callback functions.
+ *
+ * If an extant superblock is matched, then that will be returned with an
+ * elevated reference count that the caller must transfer or discard.
+ *
+ * If no match is made, a new superblock will be allocated and basic
+ * initialisation will be performed (s_type, s_fs_info and s_id will be set and
+ * the set() callback will be invoked), the superblock will be published and it
+ * will be returned in a partially constructed state with SB_BORN and SB_ACTIVE
+ * as yet unset.
+ */
+struct super_block *sget_fc(struct fs_context *fc,
+ int (*test)(struct super_block *, struct fs_context *),
+ int (*set)(struct super_block *, struct fs_context *))
+{
+ struct super_block *s = NULL;
+ struct super_block *old;
+ int err;
+
+ if (!(fc->sb_flags & SB_KERNMOUNT) &&
+ fc->purpose != FS_CONTEXT_FOR_SUBMOUNT) {
+ /* Don't allow mounting unless the caller has CAP_SYS_ADMIN
+ * over the namespace.
+ */
+ if (!(fc->fs_type->fs_flags & FS_USERNS_MOUNT) &&
+ !capable(CAP_SYS_ADMIN))
+ return ERR_PTR(-EPERM);
+ else if (!ns_capable(fc->user_ns, CAP_SYS_ADMIN))
+ return ERR_PTR(-EPERM);
+ }
+
+retry:
+ spin_lock(&sb_lock);
+ if (test) {
+ hlist_for_each_entry(old, &fc->fs_type->fs_supers, s_instances) {
+ if (!test(old, fc))
+ continue;
+ if (fc->user_ns != old->s_user_ns) {
+ spin_unlock(&sb_lock);
+ if (s) {
+ up_write(&s->s_umount);
+ destroy_unused_super(s);
+ }
+ return ERR_PTR(-EBUSY);
+ }
+ if (!grab_super(old))
+ goto retry;
+ if (s) {
+ up_write(&s->s_umount);
+ destroy_unused_super(s);
+ s = NULL;
+ }
+ return old;
+ }
+ }
+ if (!s) {
+ spin_unlock(&sb_lock);
+ s = alloc_super(fc);
+ if (!s)
+ return ERR_PTR(-ENOMEM);
+ goto retry;
+ }
+
+ s->s_fs_info = fc->s_fs_info;
+ err = set(s, fc);
+ if (err) {
+ s->s_fs_info = NULL;
+ spin_unlock(&sb_lock);
+ up_write(&s->s_umount);
+ destroy_unused_super(s);
+ return ERR_PTR(err);
+ }
+ fc->s_fs_info = NULL;
+ s->s_type = fc->fs_type;
+ strlcpy(s->s_id, s->s_type->name, sizeof(s->s_id));
+ list_add_tail(&s->s_list, &super_blocks);
+ hlist_add_head(&s->s_instances, &s->s_type->fs_supers);
+ spin_unlock(&sb_lock);
+ get_filesystem(s->s_type);
+ register_shrinker(&s->s_shrink);
+ return s;
+}
+EXPORT_SYMBOL(sget_fc);
+
/**
* sget_userns - find or create a superblock
* @type: filesystem type superblock should belong to
@@ -514,7 +603,14 @@ struct super_block *sget_userns(struct file_system_type *type,
}
if (!s) {
spin_unlock(&sb_lock);
- s = alloc_super(type, (flags & ~SB_SUBMOUNT), user_ns);
+ {
+ struct fs_context fc = {
+ .fs_type = type,
+ .sb_flags = flags & ~SB_SUBMOUNT,
+ .user_ns = user_ns,
+ };
+ s = alloc_super(&fc);
+ }
if (!s)
return ERR_PTR(-ENOMEM);
goto retry;
@@ -838,11 +934,13 @@ struct super_block *user_get_super(dev_t dev)
* @data: the rest of options
* @data_size: The size of the data
* @force: whether or not to force the change
+ * @fc: the superblock config 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 sb_flags, void *data,
- size_t data_size, int force)
+ size_t data_size, int force, struct fs_context *fc)
{
int retval;
int remount_ro;
@@ -884,8 +982,17 @@ int do_remount_sb(struct super_block *sb, int sb_flags, void *data,
}
}
- if (sb->s_op->remount_fs) {
- retval = sb->s_op->remount_fs(sb, &sb_flags, data, data_size);
+ if (sb->s_op->reconfigure ||
+ sb->s_op->remount_fs) {
+ if (sb->s_op->reconfigure) {
+ retval = sb->s_op->reconfigure(sb, fc);
+ sb_flags = fc->sb_flags;
+ if (retval == 0)
+ security_sb_reconfigure(fc);
+ } else {
+ retval = sb->s_op->remount_fs(sb, &sb_flags,
+ data, data_size);
+ }
if (retval) {
if (!force)
goto cancel_readonly;
@@ -924,7 +1031,7 @@ static void do_emergency_remount_callback(struct super_block *sb)
/*
* What lock protects sb->s_flags??
*/
- do_remount_sb(sb, SB_RDONLY, NULL, 0, 1);
+ do_remount_sb(sb, SB_RDONLY, NULL, 0, 1, NULL);
}
up_write(&sb->s_umount);
}
@@ -1106,6 +1213,89 @@ struct dentry *mount_ns(struct file_system_type *fs_type,
EXPORT_SYMBOL(mount_ns);
+static int set_anon_super_fc(struct super_block *sb, struct fs_context *fc)
+{
+ return set_anon_super(sb, NULL);
+}
+
+static int test_keyed_super(struct super_block *sb, struct fs_context *fc)
+{
+ return sb->s_fs_info == fc->s_fs_info;
+}
+
+static int test_single_super(struct super_block *s, struct fs_context *fc)
+{
+ return 1;
+}
+
+/**
+ * vfs_get_super - Get a superblock with a search key set in s_fs_info.
+ * @fc: The filesystem context holding the parameters
+ * @keying: How to distinguish superblocks
+ * @fill_super: Helper to initialise a new superblock
+ *
+ * Search for a superblock and create a new one if not found. The search
+ * criterion is controlled by @keying. If the search fails, a new superblock
+ * is created and @fill_super() is called to initialise it.
+ *
+ * @keying can take one of a number of values:
+ *
+ * (1) vfs_get_single_super - Only one superblock of this type may exist on the
+ * system. This is typically used for special system filesystems.
+ *
+ * (2) vfs_get_keyed_super - Multiple superblocks may exist, but they must have
+ * distinct keys (where the key is in s_fs_info). Searching for the same
+ * key again will turn up the superblock for that key.
+ *
+ * (3) vfs_get_independent_super - Multiple superblocks may exist and are
+ * unkeyed. Each call will get a new superblock.
+ *
+ * A permissions check is made by sget_fc() unless we're getting a superblock
+ * for a kernel-internal mount or a submount.
+ */
+int vfs_get_super(struct fs_context *fc,
+ enum vfs_get_super_keying keying,
+ int (*fill_super)(struct super_block *sb,
+ struct fs_context *fc))
+{
+ int (*test)(struct super_block *, struct fs_context *);
+ struct super_block *sb;
+
+ switch (keying) {
+ case vfs_get_single_super:
+ test = test_single_super;
+ break;
+ case vfs_get_keyed_super:
+ test = test_keyed_super;
+ break;
+ case vfs_get_independent_super:
+ test = NULL;
+ break;
+ default:
+ BUG();
+ }
+
+ sb = sget_fc(fc, test, set_anon_super_fc);
+ if (IS_ERR(sb))
+ return PTR_ERR(sb);
+
+ if (!sb->s_root) {
+ int err = fill_super(sb, fc);
+ if (err) {
+ deactivate_locked_super(sb);
+ return err;
+ }
+
+ sb->s_flags |= SB_ACTIVE;
+ }
+
+ BUG_ON(fc->root);
+ fc->root = dget(sb->s_root);
+ fc->drop_sb = true;
+ return 0;
+}
+EXPORT_SYMBOL(vfs_get_super);
+
#ifdef CONFIG_BLOCK
static int set_bdev_super(struct super_block *s, void *data)
{
@@ -1254,7 +1444,7 @@ struct dentry *mount_single(struct file_system_type *fs_type,
}
s->s_flags |= SB_ACTIVE;
} else {
- do_remount_sb(s, flags, data, data_size, 0);
+ do_remount_sb(s, flags, data, data_size, 0, NULL);
}
return dget(s->s_root);
}
@@ -1601,3 +1791,90 @@ int thaw_super(struct super_block *sb)
return thaw_super_locked(sb);
}
EXPORT_SYMBOL(thaw_super);
+
+/**
+ * vfs_get_tree - Get the mountable root
+ * @fc: The superblock configuration context.
+ *
+ * The filesystem is invoked to get or create a superblock which can then later
+ * be used for mounting. The filesystem places a pointer to the root to be
+ * used for mounting in @fc->root.
+ */
+int vfs_get_tree(struct fs_context *fc)
+{
+ struct super_block *sb;
+ int ret;
+
+ if (fc->fs_type->fs_flags & FS_REQUIRES_DEV && !fc->source)
+ return -ENOENT;
+
+ if (fc->root)
+ return -EBUSY;
+
+ if (fc->ops->validate) {
+ ret = fc->ops->validate(fc);
+ if (ret < 0)
+ return ret;
+ }
+
+ ret = security_fs_context_validate(fc);
+ if (ret < 0)
+ return ret;
+
+ /* Get the mountable root in fc->root, with a ref on the root and a ref
+ * on the superblock.
+ */
+ ret = fc->ops->get_tree(fc);
+ if (ret < 0)
+ return ret;
+
+ if (!fc->root) {
+ pr_err("Filesystem %s get_tree() didn't set fc->root\n",
+ fc->fs_type->name);
+ /* We don't know what the locking state of the superblock is -
+ * if there is a superblock.
+ */
+ BUG();
+ }
+
+ sb = fc->root->d_sb;
+ WARN_ON(!sb->s_bdi);
+
+ ret = security_sb_get_tree(fc);
+ if (ret < 0)
+ goto err_sb;
+
+ ret = -ENOMEM;
+ if (fc->subtype && !sb->s_subtype) {
+ sb->s_subtype = kstrdup(fc->subtype, GFP_KERNEL);
+ if (!sb->s_subtype)
+ goto err_sb;
+ }
+
+ /* Write barrier is for super_cache_count(). We place it before setting
+ * SB_BORN as the data dependency between the two functions is the
+ * superblock structure contents that we just set up, not the SB_BORN
+ * flag.
+ */
+ smp_wmb();
+ sb->s_flags |= SB_BORN;
+
+ /* 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",
+ fc->fs_type->name, sb->s_maxbytes);
+
+ up_write(&sb->s_umount);
+ return 0;
+
+err_sb:
+ dput(fc->root);
+ fc->root = NULL;
+ deactivate_locked_super(sb);
+ return ret;
+}
+EXPORT_SYMBOL(vfs_get_tree);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index f7bb71b8e3df..19bbed58829d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -60,6 +60,7 @@ struct workqueue_struct;
struct iov_iter;
struct fscrypt_info;
struct fscrypt_operations;
+struct fs_context;
extern void __init inode_init(void);
extern void __init inode_init_early(void);
@@ -718,6 +719,11 @@ 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);
@@ -1828,6 +1834,7 @@ struct super_operations {
int (*unfreeze_fs) (struct super_block *);
int (*statfs) (struct dentry *, struct kstatfs *);
int (*remount_fs) (struct super_block *, int *, char *, size_t);
+ int (*reconfigure) (struct super_block *, struct fs_context *);
void (*umount_begin) (struct super_block *);
int (*show_options)(struct seq_file *, struct dentry *);
@@ -2074,6 +2081,7 @@ 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. */
+ int (*init_fs_context)(struct fs_context *, struct dentry *);
struct dentry *(*mount) (struct file_system_type *, int,
const char *, void *, size_t);
void (*kill_sb) (struct super_block *);
@@ -2132,6 +2140,9 @@ void deactivate_locked_super(struct super_block *sb);
int set_anon_super(struct super_block *s, void *data);
int get_anon_bdev(dev_t *);
void free_anon_bdev(dev_t);
+struct super_block *sget_fc(struct fs_context *fc,
+ int (*test)(struct super_block *, struct fs_context *),
+ int (*set)(struct super_block *, struct fs_context *));
struct super_block *sget_userns(struct file_system_type *type,
int (*test)(struct super_block *,void *),
int (*set)(struct super_block *,void *),
@@ -2174,8 +2185,8 @@ mount_pseudo(struct file_system_type *fs_type, char *name,
extern int register_filesystem(struct file_system_type *);
extern int unregister_filesystem(struct file_system_type *);
+extern struct vfsmount *kern_mount(struct file_system_type *);
extern struct vfsmount *kern_mount_data(struct file_system_type *, void *, size_t);
-#define kern_mount(type) kern_mount_data(type, NULL, 0)
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/fs_context.h b/include/linux/fs_context.h
index 04783814632c..368fe5bb1efd 100644
--- a/include/linux/fs_context.h
+++ b/include/linux/fs_context.h
@@ -25,6 +25,7 @@ struct pid_namespace;
struct super_block;
struct user_namespace;
struct vfsmount;
+struct path;
enum fs_context_purpose {
FS_CONTEXT_FOR_USER_MOUNT, /* New superblock for user-specified mount */
@@ -33,6 +34,19 @@ enum fs_context_purpose {
FS_CONTEXT_FOR_RECONFIGURE, /* Superblock reconfiguration (remount) */
};
+/*
+ * Userspace usage phase for fsopen/fspick.
+ */
+enum fs_context_phase {
+ FS_CONTEXT_CREATE_PARAMS, /* Loading params for sb creation */
+ FS_CONTEXT_CREATING, /* A superblock is being created */
+ FS_CONTEXT_AWAITING_MOUNT, /* Superblock created, awaiting fsmount() */
+ FS_CONTEXT_AWAITING_RECONF, /* Awaiting initialisation for reconfiguration */
+ FS_CONTEXT_RECONF_PARAMS, /* Loading params for reconfiguration */
+ FS_CONTEXT_RECONFIGURING, /* Reconfiguring the superblock */
+ FS_CONTEXT_FAILED, /* Failed to correctly transition a context */
+};
+
/*
* Filesystem context for holding the parameters used in the creation or
* reconfiguration of a superblock.
@@ -60,6 +74,7 @@ struct fs_context {
bool drop_sb:1; /* T if need to drop an SB reference */
bool source_is_dev:1; /* T if source is local device/file */
enum fs_context_purpose purpose : 8;
+ enum fs_context_phase phase:8; /* The phase the context is in */
};
struct fs_context_operations {
@@ -67,9 +82,37 @@ struct fs_context_operations {
int (*dup)(struct fs_context *fc, struct fs_context *src_fc);
int (*parse_source)(struct fs_context *fc, char *source);
int (*parse_option)(struct fs_context *fc, char *opt, size_t len);
- int (*parse_monolithic)(struct fs_context *fc, void *data);
+ int (*parse_monolithic)(struct fs_context *fc, void *data, size_t data_size);
int (*validate)(struct fs_context *fc);
int (*get_tree)(struct fs_context *fc);
};
+/*
+ * fs_context manipulation functions.
+ */
+extern struct fs_context *vfs_new_fs_context(struct file_system_type *fs_type,
+ struct dentry *reference,
+ unsigned int ms_flags,
+ enum fs_context_purpose purpose);
+extern struct fs_context *vfs_sb_reconfig(struct path *path, unsigned int ms_flags);
+extern struct fs_context *vfs_dup_fs_context(struct fs_context *src);
+extern int vfs_set_fs_source(struct fs_context *fc, const char *source, size_t slen);
+extern int vfs_parse_fs_option(struct fs_context *fc, char *data, size_t opt);
+extern int generic_parse_monolithic(struct fs_context *fc, void *data, size_t data_size);
+extern int vfs_get_tree(struct fs_context *fc);
+extern void put_fs_context(struct fs_context *fc);
+
+/*
+ * sget() wrapper to be called from the ->get_tree() op.
+ */
+enum vfs_get_super_keying {
+ vfs_get_single_super, /* Only one such superblock may exist */
+ vfs_get_keyed_super, /* Superblocks with different s_fs_info keys may exist */
+ vfs_get_independent_super, /* Multiple independent superblocks may exist */
+};
+extern int vfs_get_super(struct fs_context *fc,
+ enum vfs_get_super_keying keying,
+ int (*fill_super)(struct super_block *sb,
+ struct fs_context *fc));
+
#endif /* _LINUX_FS_CONTEXT_H */
diff --git a/include/linux/mount.h b/include/linux/mount.h
index 8a1031a511c9..ee5af77afc06 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -21,6 +21,7 @@ struct super_block;
struct vfsmount;
struct dentry;
struct mnt_namespace;
+struct fs_context;
#define MNT_NOSUID 0x01
#define MNT_NODEV 0x02
@@ -88,6 +89,8 @@ struct path;
extern struct vfsmount *clone_private_mount(const struct path *path);
struct file_system_type;
+extern struct vfsmount *vfs_create_mount(struct fs_context *fc,
+ unsigned int mnt_flags);
extern struct vfsmount *vfs_kern_mount(struct file_system_type *type,
int flags, const char *name,
void *data, size_t data_size);