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linux-next/fs/fs_context.c
David Howells e7582e16a1 vfs: Implement logging through fs_context
Implement the ability for filesystems to log error, warning and
informational messages through the fs_context.  In the future, these will
be extractable by userspace by reading from an fd created by the fsopen()
syscall.

Error messages are prefixed with "e ", warnings with "w " and informational
messages with "i ".

In the future, inside the kernel, formatted messages will be malloc'd but
unformatted messages will not copied if they're either in the core .rodata
section or in the .rodata section of the filesystem module pinned by
fs_context::fs_type.  The messages will only be good till the fs_type is
released.

Note that the logging object will be shared between duplicated fs_context
structures.  This is so that such as NFS which do a mount within a mount
can get at least some of the errors from the inner mount.

Five logging functions are provided for this:

 (1) void logfc(struct fs_context *fc, const char *fmt, ...);

     This logs a message into the context.  If the buffer is full, the
     earliest message is discarded.

 (2) void errorf(fc, fmt, ...);

     This wraps logfc() to log an error.

 (3) void invalf(fc, fmt, ...);

     This wraps errorf() and returns -EINVAL for convenience.

 (4) void warnf(fc, fmt, ...);

     This wraps logfc() to log a warning.

 (5) void infof(fc, fmt, ...);

     This wraps logfc() to log an informational message.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2019-02-28 03:29:37 -05:00

643 lines
16 KiB
C

/* 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)
*
* 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_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 "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);
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:
/* We don't pin any namespaces as the superblock's
* subscriptions cannot be changed at this point.
*/
atomic_inc(&reference->d_sb->s_active);
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);
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);
/* 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);
#ifdef CONFIG_PRINTK
/**
* 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, ...)
{
va_list va;
va_start(va, fmt);
switch (fmt[0]) {
case 'w':
vprintk_emit(0, LOGLEVEL_WARNING, NULL, 0, fmt, va);
break;
case 'e':
vprintk_emit(0, LOGLEVEL_ERR, NULL, 0, fmt, va);
break;
default:
vprintk_emit(0, LOGLEVEL_NOTICE, NULL, 0, fmt, va);
break;
}
pr_cont("\n");
va_end(va);
}
EXPORT_SYMBOL(logfc);
#endif
/**
* 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);
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 = 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 ((fc->fs_type->fs_flags & FS_HAS_SUBTYPE) &&
strcmp(param->key, "subtype") == 0) {
if (param->type != fs_value_is_string)
return invalf(fc, "VFS: Legacy: Non-string subtype");
if (fc->subtype)
return invalf(fc, "VFS: Legacy: Multiple subtype");
fc->subtype = 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);
}