linux-stable/fs/fs_context.c
David Howells c7eb686963 vfs: subtype handling moved to fuse
The unused vfs code can be removed.  Don't pass empty subtype (same as if
->parse callback isn't called).

The bits that are left involve determining whether it's permitted to split the
filesystem type string passed in to mount(2).  Consequently, this means that we
cannot get rid of the FS_HAS_SUBTYPE flag unless we define that a type string
with a dot in it always indicates a subtype specification.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2019-09-06 21:28:49 +02:00

754 lines
18 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/* 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@redhat.com)
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/fs_context.h>
#include <linux/fs_parser.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/mnt_namespace.h>
#include <linux/pid_namespace.h>
#include <linux/user_namespace.h>
#include <net/net_namespace.h>
#include <asm/sections.h>
#include "mount.h"
#include "internal.h"
enum legacy_fs_param {
LEGACY_FS_UNSET_PARAMS,
LEGACY_FS_MONOLITHIC_PARAMS,
LEGACY_FS_INDIVIDUAL_PARAMS,
};
struct legacy_fs_context {
char *legacy_data; /* Data page for legacy filesystems */
size_t data_size;
enum legacy_fs_param param_type;
};
static int legacy_init_fs_context(struct fs_context *fc);
static const struct constant_table common_set_sb_flag[] = {
{ "dirsync", SB_DIRSYNC },
{ "lazytime", SB_LAZYTIME },
{ "mand", SB_MANDLOCK },
{ "posixacl", SB_POSIXACL },
{ "ro", SB_RDONLY },
{ "sync", SB_SYNCHRONOUS },
};
static const struct constant_table common_clear_sb_flag[] = {
{ "async", SB_SYNCHRONOUS },
{ "nolazytime", SB_LAZYTIME },
{ "nomand", SB_MANDLOCK },
{ "rw", SB_RDONLY },
{ "silent", SB_SILENT },
};
static const char *const forbidden_sb_flag[] = {
"bind",
"dev",
"exec",
"move",
"noatime",
"nodev",
"nodiratime",
"noexec",
"norelatime",
"nostrictatime",
"nosuid",
"private",
"rec",
"relatime",
"remount",
"shared",
"slave",
"strictatime",
"suid",
"unbindable",
};
/*
* Check for a common mount option that manipulates s_flags.
*/
static int vfs_parse_sb_flag(struct fs_context *fc, const char *key)
{
unsigned int token;
unsigned int i;
for (i = 0; i < ARRAY_SIZE(forbidden_sb_flag); i++)
if (strcmp(key, forbidden_sb_flag[i]) == 0)
return -EINVAL;
token = lookup_constant(common_set_sb_flag, key, 0);
if (token) {
fc->sb_flags |= token;
fc->sb_flags_mask |= token;
return 0;
}
token = lookup_constant(common_clear_sb_flag, key, 0);
if (token) {
fc->sb_flags &= ~token;
fc->sb_flags_mask |= token;
return 0;
}
return -ENOPARAM;
}
/**
* vfs_parse_fs_param - Add a single parameter to a superblock config
* @fc: The filesystem context to modify
* @param: The parameter
*
* 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_param(struct fs_context *fc, struct fs_parameter *param)
{
int ret;
if (!param->key)
return invalf(fc, "Unnamed parameter\n");
ret = vfs_parse_sb_flag(fc, param->key);
if (ret != -ENOPARAM)
return ret;
ret = security_fs_context_parse_param(fc, param);
if (ret != -ENOPARAM)
/* Param belongs to the LSM or is disallowed by the LSM; so
* don't pass to the FS.
*/
return ret;
if (fc->ops->parse_param) {
ret = fc->ops->parse_param(fc, param);
if (ret != -ENOPARAM)
return ret;
}
/* If the filesystem doesn't take any arguments, give it the
* default handling of source.
*/
if (strcmp(param->key, "source") == 0) {
if (param->type != fs_value_is_string)
return invalf(fc, "VFS: Non-string source");
if (fc->source)
return invalf(fc, "VFS: Multiple sources");
fc->source = param->string;
param->string = NULL;
return 0;
}
return invalf(fc, "%s: Unknown parameter '%s'",
fc->fs_type->name, param->key);
}
EXPORT_SYMBOL(vfs_parse_fs_param);
/**
* vfs_parse_fs_string - Convenience function to just parse a string.
*/
int vfs_parse_fs_string(struct fs_context *fc, const char *key,
const char *value, size_t v_size)
{
int ret;
struct fs_parameter param = {
.key = key,
.type = fs_value_is_string,
.size = v_size,
};
if (v_size > 0) {
param.string = kmemdup_nul(value, v_size, GFP_KERNEL);
if (!param.string)
return -ENOMEM;
}
ret = vfs_parse_fs_param(fc, &param);
kfree(param.string);
return ret;
}
EXPORT_SYMBOL(vfs_parse_fs_string);
/**
* generic_parse_monolithic - Parse key[=val][,key[=val]]* mount data
* @ctx: The superblock configuration to fill in.
* @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() 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)
{
char *options = data, *key;
int ret = 0;
if (!options)
return 0;
ret = security_sb_eat_lsm_opts(options, &fc->security);
if (ret)
return ret;
while ((key = strsep(&options, ",")) != NULL) {
if (*key) {
size_t v_len = 0;
char *value = strchr(key, '=');
if (value) {
if (value == key)
continue;
*value++ = 0;
v_len = strlen(value);
}
ret = vfs_parse_fs_string(fc, key, value, v_len);
if (ret < 0)
break;
}
}
return ret;
}
EXPORT_SYMBOL(generic_parse_monolithic);
/**
* alloc_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_*)
* @sb_flags_mask: Applicable members of @sb_flags
* @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.
*/
static struct fs_context *alloc_fs_context(struct file_system_type *fs_type,
struct dentry *reference,
unsigned int sb_flags,
unsigned int sb_flags_mask,
enum fs_context_purpose purpose)
{
int (*init_fs_context)(struct fs_context *);
struct fs_context *fc;
int ret = -ENOMEM;
fc = kzalloc(sizeof(struct fs_context), GFP_KERNEL);
if (!fc)
return ERR_PTR(-ENOMEM);
fc->purpose = purpose;
fc->sb_flags = sb_flags;
fc->sb_flags_mask = sb_flags_mask;
fc->fs_type = get_filesystem(fs_type);
fc->cred = get_current_cred();
fc->net_ns = get_net(current->nsproxy->net_ns);
mutex_init(&fc->uapi_mutex);
switch (purpose) {
case FS_CONTEXT_FOR_MOUNT:
fc->user_ns = get_user_ns(fc->cred->user_ns);
break;
case FS_CONTEXT_FOR_SUBMOUNT:
fc->user_ns = get_user_ns(reference->d_sb->s_user_ns);
break;
case FS_CONTEXT_FOR_RECONFIGURE:
atomic_inc(&reference->d_sb->s_active);
fc->user_ns = get_user_ns(reference->d_sb->s_user_ns);
fc->root = dget(reference);
break;
}
/* TODO: Make all filesystems support this unconditionally */
init_fs_context = fc->fs_type->init_fs_context;
if (!init_fs_context)
init_fs_context = legacy_init_fs_context;
ret = init_fs_context(fc);
if (ret < 0)
goto err_fc;
fc->need_free = true;
return fc;
err_fc:
put_fs_context(fc);
return ERR_PTR(ret);
}
struct fs_context *fs_context_for_mount(struct file_system_type *fs_type,
unsigned int sb_flags)
{
return alloc_fs_context(fs_type, NULL, sb_flags, 0,
FS_CONTEXT_FOR_MOUNT);
}
EXPORT_SYMBOL(fs_context_for_mount);
struct fs_context *fs_context_for_reconfigure(struct dentry *dentry,
unsigned int sb_flags,
unsigned int sb_flags_mask)
{
return alloc_fs_context(dentry->d_sb->s_type, dentry, sb_flags,
sb_flags_mask, FS_CONTEXT_FOR_RECONFIGURE);
}
EXPORT_SYMBOL(fs_context_for_reconfigure);
struct fs_context *fs_context_for_submount(struct file_system_type *type,
struct dentry *reference)
{
return alloc_fs_context(type, reference, 0, 0, FS_CONTEXT_FOR_SUBMOUNT);
}
EXPORT_SYMBOL(fs_context_for_submount);
void fc_drop_locked(struct fs_context *fc)
{
struct super_block *sb = fc->root->d_sb;
dput(fc->root);
fc->root = NULL;
deactivate_locked_super(sb);
}
static void legacy_fs_context_free(struct fs_context *fc);
/**
* vfs_dup_fc_config: Duplicate a filesystem 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(-EOPNOTSUPP);
fc = kmemdup(src_fc, sizeof(struct fs_context), GFP_KERNEL);
if (!fc)
return ERR_PTR(-ENOMEM);
mutex_init(&fc->uapi_mutex);
fc->fs_private = NULL;
fc->s_fs_info = 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);
if (fc->log)
refcount_inc(&fc->log->usage);
/* 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);
/**
* logfc - Log a message to a filesystem context
* @fc: The filesystem context to log to.
* @fmt: The format of the buffer.
*/
void logfc(struct fs_context *fc, const char *fmt, ...)
{
static const char store_failure[] = "OOM: Can't store error string";
struct fc_log *log = fc ? fc->log : NULL;
const char *p;
va_list va;
char *q;
u8 freeable;
va_start(va, fmt);
if (!strchr(fmt, '%')) {
p = fmt;
goto unformatted_string;
}
if (strcmp(fmt, "%s") == 0) {
p = va_arg(va, const char *);
goto unformatted_string;
}
q = kvasprintf(GFP_KERNEL, fmt, va);
copied_string:
if (!q)
goto store_failure;
freeable = 1;
goto store_string;
unformatted_string:
if ((unsigned long)p >= (unsigned long)__start_rodata &&
(unsigned long)p < (unsigned long)__end_rodata)
goto const_string;
if (log && within_module_core((unsigned long)p, log->owner))
goto const_string;
q = kstrdup(p, GFP_KERNEL);
goto copied_string;
store_failure:
p = store_failure;
const_string:
q = (char *)p;
freeable = 0;
store_string:
if (!log) {
switch (fmt[0]) {
case 'w':
printk(KERN_WARNING "%s\n", q + 2);
break;
case 'e':
printk(KERN_ERR "%s\n", q + 2);
break;
default:
printk(KERN_NOTICE "%s\n", q + 2);
break;
}
if (freeable)
kfree(q);
} else {
unsigned int logsize = ARRAY_SIZE(log->buffer);
u8 index;
index = log->head & (logsize - 1);
BUILD_BUG_ON(sizeof(log->head) != sizeof(u8) ||
sizeof(log->tail) != sizeof(u8));
if ((u8)(log->head - log->tail) == logsize) {
/* The buffer is full, discard the oldest message */
if (log->need_free & (1 << index))
kfree(log->buffer[index]);
log->tail++;
}
log->buffer[index] = q;
log->need_free &= ~(1 << index);
log->need_free |= freeable << index;
log->head++;
}
va_end(va);
}
EXPORT_SYMBOL(logfc);
/*
* Free a logging structure.
*/
static void put_fc_log(struct fs_context *fc)
{
struct fc_log *log = fc->log;
int i;
if (log) {
if (refcount_dec_and_test(&log->usage)) {
fc->log = NULL;
for (i = 0; i <= 7; i++)
if (log->need_free & (1 << i))
kfree(log->buffer[i]);
kfree(log);
}
}
}
/**
* 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;
deactivate_super(sb);
}
if (fc->need_free && fc->ops && fc->ops->free)
fc->ops->free(fc);
security_free_mnt_opts(&fc->security);
put_net(fc->net_ns);
put_user_ns(fc->user_ns);
put_cred(fc->cred);
put_fc_log(fc);
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 = fc->fs_private;
if (ctx) {
if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS)
kfree(ctx->legacy_data);
kfree(ctx);
}
}
/*
* Duplicate a legacy config.
*/
static int legacy_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc)
{
struct legacy_fs_context *ctx;
struct legacy_fs_context *src_ctx = src_fc->fs_private;
ctx = kmemdup(src_ctx, sizeof(*src_ctx), GFP_KERNEL);
if (!ctx)
return -ENOMEM;
if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS) {
ctx->legacy_data = kmemdup(src_ctx->legacy_data,
src_ctx->data_size, GFP_KERNEL);
if (!ctx->legacy_data) {
kfree(ctx);
return -ENOMEM;
}
}
fc->fs_private = ctx;
return 0;
}
/*
* Add a parameter to a legacy config. We build up a comma-separated list of
* options.
*/
static int legacy_parse_param(struct fs_context *fc, struct fs_parameter *param)
{
struct legacy_fs_context *ctx = fc->fs_private;
unsigned int size = ctx->data_size;
size_t len = 0;
if (strcmp(param->key, "source") == 0) {
if (param->type != fs_value_is_string)
return invalf(fc, "VFS: Legacy: Non-string source");
if (fc->source)
return invalf(fc, "VFS: Legacy: Multiple sources");
fc->source = param->string;
param->string = NULL;
return 0;
}
if (ctx->param_type == LEGACY_FS_MONOLITHIC_PARAMS)
return invalf(fc, "VFS: Legacy: Can't mix monolithic and individual options");
switch (param->type) {
case fs_value_is_string:
len = 1 + param->size;
/* Fall through */
case fs_value_is_flag:
len += strlen(param->key);
break;
default:
return invalf(fc, "VFS: Legacy: Parameter type for '%s' not supported",
param->key);
}
if (len > PAGE_SIZE - 2 - size)
return invalf(fc, "VFS: Legacy: Cumulative options too large");
if (strchr(param->key, ',') ||
(param->type == fs_value_is_string &&
memchr(param->string, ',', param->size)))
return invalf(fc, "VFS: Legacy: Option '%s' contained comma",
param->key);
if (!ctx->legacy_data) {
ctx->legacy_data = kmalloc(PAGE_SIZE, GFP_KERNEL);
if (!ctx->legacy_data)
return -ENOMEM;
}
ctx->legacy_data[size++] = ',';
len = strlen(param->key);
memcpy(ctx->legacy_data + size, param->key, len);
size += len;
if (param->type == fs_value_is_string) {
ctx->legacy_data[size++] = '=';
memcpy(ctx->legacy_data + size, param->string, param->size);
size += param->size;
}
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)
{
struct legacy_fs_context *ctx = fc->fs_private;
if (ctx->param_type != LEGACY_FS_UNSET_PARAMS) {
pr_warn("VFS: Can't mix monolithic and individual options\n");
return -EINVAL;
}
ctx->legacy_data = data;
ctx->param_type = LEGACY_FS_MONOLITHIC_PARAMS;
if (!ctx->legacy_data)
return 0;
if (fc->fs_type->fs_flags & FS_BINARY_MOUNTDATA)
return 0;
return security_sb_eat_lsm_opts(ctx->legacy_data, &fc->security);
}
/*
* Get a mountable root with the legacy mount command.
*/
static int legacy_get_tree(struct fs_context *fc)
{
struct legacy_fs_context *ctx = fc->fs_private;
struct super_block *sb;
struct dentry *root;
root = fc->fs_type->mount(fc->fs_type, fc->sb_flags,
fc->source, ctx->legacy_data);
if (IS_ERR(root))
return PTR_ERR(root);
sb = root->d_sb;
BUG_ON(!sb);
fc->root = root;
return 0;
}
/*
* Handle remount.
*/
static int legacy_reconfigure(struct fs_context *fc)
{
struct legacy_fs_context *ctx = fc->fs_private;
struct super_block *sb = fc->root->d_sb;
if (!sb->s_op->remount_fs)
return 0;
return sb->s_op->remount_fs(sb, &fc->sb_flags,
ctx ? ctx->legacy_data : NULL);
}
const struct fs_context_operations legacy_fs_context_ops = {
.free = legacy_fs_context_free,
.dup = legacy_fs_context_dup,
.parse_param = legacy_parse_param,
.parse_monolithic = legacy_parse_monolithic,
.get_tree = legacy_get_tree,
.reconfigure = legacy_reconfigure,
};
/*
* Initialise a legacy context for a filesystem that doesn't support
* fs_context.
*/
static int legacy_init_fs_context(struct fs_context *fc)
{
fc->fs_private = kzalloc(sizeof(struct legacy_fs_context), GFP_KERNEL);
if (!fc->fs_private)
return -ENOMEM;
fc->ops = &legacy_fs_context_ops;
return 0;
}
int parse_monolithic_mount_data(struct fs_context *fc, void *data)
{
int (*monolithic_mount_data)(struct fs_context *, void *);
monolithic_mount_data = fc->ops->parse_monolithic;
if (!monolithic_mount_data)
monolithic_mount_data = generic_parse_monolithic;
return monolithic_mount_data(fc, data);
}
/*
* Clean up a context after performing an action on it and put it into a state
* from where it can be used to reconfigure a superblock.
*
* Note that here we do only the parts that can't fail; the rest is in
* finish_clean_context() below and in between those fs_context is marked
* FS_CONTEXT_AWAITING_RECONF. The reason for splitup is that after
* successful mount or remount we need to report success to userland.
* Trying to do full reinit (for the sake of possible subsequent remount)
* and failing to allocate memory would've put us into a nasty situation.
* So here we only discard the old state and reinitialization is left
* until we actually try to reconfigure.
*/
void vfs_clean_context(struct fs_context *fc)
{
if (fc->need_free && fc->ops && fc->ops->free)
fc->ops->free(fc);
fc->need_free = false;
fc->fs_private = NULL;
fc->s_fs_info = NULL;
fc->sb_flags = 0;
security_free_mnt_opts(&fc->security);
kfree(fc->source);
fc->source = NULL;
fc->purpose = FS_CONTEXT_FOR_RECONFIGURE;
fc->phase = FS_CONTEXT_AWAITING_RECONF;
}
int finish_clean_context(struct fs_context *fc)
{
int error;
if (fc->phase != FS_CONTEXT_AWAITING_RECONF)
return 0;
if (fc->fs_type->init_fs_context)
error = fc->fs_type->init_fs_context(fc);
else
error = legacy_init_fs_context(fc);
if (unlikely(error)) {
fc->phase = FS_CONTEXT_FAILED;
return error;
}
fc->need_free = true;
fc->phase = FS_CONTEXT_RECONF_PARAMS;
return 0;
}