include/linux/fs_context.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /* Filesystem superblock creation and reconfiguration context.
   3  *
   4  * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #ifndef _LINUX_FS_CONTEXT_H
   9 #define _LINUX_FS_CONTEXT_H
  10
  11 #include <linux/kernel.h>
  12 #include <linux/refcount.h>
  13 #include <linux/errno.h>
  14 #include <linux/security.h>
  15 #include <linux/mutex.h>
  16
  17 struct cred;
  18 struct dentry;
  19 struct file_operations;
  20 struct file_system_type;
  21 struct mnt_namespace;
  22 struct net;
  23 struct pid_namespace;
  24 struct super_block;
  25 struct user_namespace;
  26 struct vfsmount;
  27 struct path;
  28
  29 enum fs_context_purpose {
  30         FS_CONTEXT_FOR_MOUNT,           /* New superblock for explicit mount */
  31         FS_CONTEXT_FOR_SUBMOUNT,        /* New superblock for automatic submount */
  32         FS_CONTEXT_FOR_RECONFIGURE,     /* Superblock reconfiguration (remount) */
  33 };
  34
  35 /*
  36  * Userspace usage phase for fsopen/fspick.
  37  */
  38 enum fs_context_phase {
  39         FS_CONTEXT_CREATE_PARAMS,       /* Loading params for sb creation */
  40         FS_CONTEXT_CREATING,            /* A superblock is being created */
  41         FS_CONTEXT_AWAITING_MOUNT,      /* Superblock created, awaiting fsmount() */
  42         FS_CONTEXT_AWAITING_RECONF,     /* Awaiting initialisation for reconfiguration */
  43         FS_CONTEXT_RECONF_PARAMS,       /* Loading params for reconfiguration */
  44         FS_CONTEXT_RECONFIGURING,       /* Reconfiguring the superblock */
  45         FS_CONTEXT_FAILED,              /* Failed to correctly transition a context */
  46 };
  47
  48 /*
  49  * Type of parameter value.
  50  */
  51 enum fs_value_type {
  52         fs_value_is_undefined,
  53         fs_value_is_flag,               /* Value not given a value */
  54         fs_value_is_string,             /* Value is a string */
  55         fs_value_is_blob,               /* Value is a binary blob */
  56         fs_value_is_filename,           /* Value is a filename* + dirfd */
  57         fs_value_is_file,               /* Value is a file* */
  58 };
  59
  60 /*
  61  * Configuration parameter.
  62  */
  63 struct fs_parameter {
  64         const char              *key;           /* Parameter name */
  65         enum fs_value_type      type:8;         /* The type of value here */
  66         union {
  67                 char            *string;
  68                 void            *blob;
  69                 struct filename *name;
  70                 struct file     *file;
  71         };
  72         size_t  size;
  73         int     dirfd;
  74 };
  75
  76 struct p_log {
  77         const char *prefix;
  78         struct fc_log *log;
  79 };
  80
  81 /*
  82  * Filesystem context for holding the parameters used in the creation or
  83  * reconfiguration of a superblock.
  84  *
  85  * Superblock creation fills in ->root whereas reconfiguration begins with this
  86  * already set.
  87  *
  88  * See Documentation/filesystems/mount_api.rst
  89  */
  90 struct fs_context {
  91         const struct fs_context_operations *ops;
  92         struct mutex            uapi_mutex;     /* Userspace access mutex */
  93         struct file_system_type *fs_type;
  94         void                    *fs_private;    /* The filesystem's context */
  95         void                    *sget_key;
  96         struct dentry           *root;          /* The root and superblock */
  97         struct user_namespace   *user_ns;       /* The user namespace for this mount */
  98         struct net              *net_ns;        /* The network namespace for this mount */
  99         const struct cred       *cred;          /* The mounter's credentials */
 100         struct p_log            log;            /* Logging buffer */
 101         const char              *source;        /* The source name (eg. dev path) */
 102         void                    *security;      /* Linux S&M options */
 103         void                    *s_fs_info;     /* Proposed s_fs_info */
 104         unsigned int            sb_flags;       /* Proposed superblock flags (SB_*) */
 105         unsigned int            sb_flags_mask;  /* Superblock flags that were changed */
 106         unsigned int            s_iflags;       /* OR'd with sb->s_iflags */
 107         unsigned int            lsm_flags;      /* Information flags from the fs to the LSM */
 108         enum fs_context_purpose purpose:8;
 109         enum fs_context_phase   phase:8;        /* The phase the context is in */
 110         bool                    need_free:1;    /* Need to call ops->free() */
 111         bool                    global:1;       /* Goes into &init_user_ns */
 112         bool                    oldapi:1;       /* Coming from mount(2) */
 113 };
 114
 115 struct fs_context_operations {
 116         void (*free)(struct fs_context *fc);
 117         int (*dup)(struct fs_context *fc, struct fs_context *src_fc);
 118         int (*parse_param)(struct fs_context *fc, struct fs_parameter *param);
 119         int (*parse_monolithic)(struct fs_context *fc, void *data);
 120         int (*get_tree)(struct fs_context *fc);
 121         int (*reconfigure)(struct fs_context *fc);
 122 };
 123
 124 /*
 125  * fs_context manipulation functions.
 126  */
 127 extern struct fs_context *fs_context_for_mount(struct file_system_type *fs_type,
 128                                                 unsigned int sb_flags);
 129 extern struct fs_context *fs_context_for_reconfigure(struct dentry *dentry,
 130                                                 unsigned int sb_flags,
 131                                                 unsigned int sb_flags_mask);
 132 extern struct fs_context *fs_context_for_submount(struct file_system_type *fs_type,
 133                                                 struct dentry *reference);
 134
 135 extern struct fs_context *vfs_dup_fs_context(struct fs_context *fc);
 136 extern int vfs_parse_fs_param(struct fs_context *fc, struct fs_parameter *param);
 137 extern int vfs_parse_fs_string(struct fs_context *fc, const char *key,
 138                                const char *value, size_t v_size);
 139 extern int generic_parse_monolithic(struct fs_context *fc, void *data);
 140 extern int vfs_get_tree(struct fs_context *fc);
 141 extern void put_fs_context(struct fs_context *fc);
 142
 143 /*
 144  * sget() wrappers to be called from the ->get_tree() op.
 145  */
 146 enum vfs_get_super_keying {
 147         vfs_get_single_super,   /* Only one such superblock may exist */
 148         vfs_get_single_reconf_super, /* As above, but reconfigure if it exists */
 149         vfs_get_keyed_super,    /* Superblocks with different s_fs_info keys may exist */
 150         vfs_get_independent_super, /* Multiple independent superblocks may exist */
 151 };
 152 extern int vfs_get_super(struct fs_context *fc,
 153                          enum vfs_get_super_keying keying,
 154                          int (*fill_super)(struct super_block *sb,
 155                                            struct fs_context *fc));
 156
 157 extern int get_tree_nodev(struct fs_context *fc,
 158                          int (*fill_super)(struct super_block *sb,
 159                                            struct fs_context *fc));
 160 extern int get_tree_single(struct fs_context *fc,
 161                          int (*fill_super)(struct super_block *sb,
 162                                            struct fs_context *fc));
 163 extern int get_tree_single_reconf(struct fs_context *fc,
 164                          int (*fill_super)(struct super_block *sb,
 165                                            struct fs_context *fc));
 166 extern int get_tree_keyed(struct fs_context *fc,
 167                          int (*fill_super)(struct super_block *sb,
 168                                            struct fs_context *fc),
 169                          void *key);
 170
 171 extern int get_tree_bdev(struct fs_context *fc,
 172                                int (*fill_super)(struct super_block *sb,
 173                                                  struct fs_context *fc));
 174
 175 extern const struct file_operations fscontext_fops;
 176
 177 /*
 178  * Mount error, warning and informational message logging.  This structure is
 179  * shareable between a mount and a subordinate mount.
 180  */
 181 struct fc_log {
 182         refcount_t      usage;
 183         u8              head;           /* Insertion index in buffer[] */
 184         u8              tail;           /* Removal index in buffer[] */
 185         u8              need_free;      /* Mask of kfree'able items in buffer[] */
 186         struct module   *owner;         /* Owner module for strings that don't then need freeing */
 187         char            *buffer[8];
 188 };
 189
 190 extern __attribute__((format(printf, 4, 5)))
 191 void logfc(struct fc_log *log, const char *prefix, char level, const char *fmt, ...);
 192
 193 #define __logfc(fc, l, fmt, ...) logfc((fc)->log.log, NULL, \
 194                                         l, fmt, ## __VA_ARGS__)
 195 #define __plog(p, l, fmt, ...) logfc((p)->log, (p)->prefix, \
 196                                         l, fmt, ## __VA_ARGS__)
 197 /**
 198  * infof - Store supplementary informational message
 199  * @fc: The context in which to log the informational message
 200  * @fmt: The format string
 201  *
 202  * Store the supplementary informational message for the process if the process
 203  * has enabled the facility.
 204  */
 205 #define infof(fc, fmt, ...) __logfc(fc, 'i', fmt, ## __VA_ARGS__)
 206 #define info_plog(p, fmt, ...) __plog(p, 'i', fmt, ## __VA_ARGS__)
 207 #define infofc(p, fmt, ...) __plog((&(fc)->log), 'i', fmt, ## __VA_ARGS__)
 208
 209 /**
 210  * warnf - Store supplementary warning message
 211  * @fc: The context in which to log the error message
 212  * @fmt: The format string
 213  *
 214  * Store the supplementary warning message for the process if the process has
 215  * enabled the facility.
 216  */
 217 #define warnf(fc, fmt, ...) __logfc(fc, 'w', fmt, ## __VA_ARGS__)
 218 #define warn_plog(p, fmt, ...) __plog(p, 'w', fmt, ## __VA_ARGS__)
 219 #define warnfc(fc, fmt, ...) __plog((&(fc)->log), 'w', fmt, ## __VA_ARGS__)
 220
 221 /**
 222  * errorf - Store supplementary error message
 223  * @fc: The context in which to log the error message
 224  * @fmt: The format string
 225  *
 226  * Store the supplementary error message for the process if the process has
 227  * enabled the facility.
 228  */
 229 #define errorf(fc, fmt, ...) __logfc(fc, 'e', fmt, ## __VA_ARGS__)
 230 #define error_plog(p, fmt, ...) __plog(p, 'e', fmt, ## __VA_ARGS__)
 231 #define errorfc(fc, fmt, ...) __plog((&(fc)->log), 'e', fmt, ## __VA_ARGS__)
 232
 233 /**
 234  * invalf - Store supplementary invalid argument error message
 235  * @fc: The context in which to log the error message
 236  * @fmt: The format string
 237  *
 238  * Store the supplementary error message for the process if the process has
 239  * enabled the facility and return -EINVAL.
 240  */
 241 #define invalf(fc, fmt, ...) (errorf(fc, fmt, ## __VA_ARGS__), -EINVAL)
 242 #define inval_plog(p, fmt, ...) (error_plog(p, fmt, ## __VA_ARGS__), -EINVAL)
 243 #define invalfc(fc, fmt, ...) (errorfc(fc, fmt, ## __VA_ARGS__), -EINVAL)
 244
 245 #endif /* _LINUX_FS_CONTEXT_H */