namei.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2#ifndef _LINUX_NAMEI_H
  3#define _LINUX_NAMEI_H
  4
  5#include <linux/fs.h>
  6#include <linux/kernel.h>
  7#include <linux/path.h>
  8#include <linux/fcntl.h>
  9#include <linux/errno.h>
 10#include <linux/fs_struct.h>
 11
 12enum { MAX_NESTED_LINKS = 8 };
 13
 14#define MAXSYMLINKS 40
 15
 16/*
 17 * Type of the last component on LOOKUP_PARENT
 18 */
 19enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT};
 20
 21/* pathwalk mode */
 22#define LOOKUP_FOLLOW		BIT(0)	/* follow links at the end */
 23#define LOOKUP_DIRECTORY	BIT(1)	/* require a directory */
 24#define LOOKUP_AUTOMOUNT	BIT(2)  /* force terminal automount */
 25#define LOOKUP_EMPTY		BIT(3)	/* accept empty path [user_... only] */
 26#define LOOKUP_LINKAT_EMPTY	BIT(4) /* Linkat request with empty path. */
 27#define LOOKUP_DOWN		BIT(5)	/* follow mounts in the starting point */
 28#define LOOKUP_MOUNTPOINT	BIT(6)	/* follow mounts in the end */
 29#define LOOKUP_REVAL		BIT(7)	/* tell ->d_revalidate() to trust no cache */
 30#define LOOKUP_RCU		BIT(8)	/* RCU pathwalk mode; semi-internal */
 31#define LOOKUP_CACHED		BIT(9) /* Only do cached lookup */
 32#define LOOKUP_PARENT		BIT(10)	/* Looking up final parent in path */
 33/* 5 spare bits for pathwalk */
 34
 35/* These tell filesystem methods that we are dealing with the final component... */
 36#define LOOKUP_OPEN		BIT(16)	/* ... in open */
 37#define LOOKUP_CREATE		BIT(17)	/* ... in object creation */
 38#define LOOKUP_EXCL		BIT(18)	/* ... in target must not exist */
 39#define LOOKUP_RENAME_TARGET	BIT(19)	/* ... in destination of rename() */
 40
 41/* 4 spare bits for intent */
 42
 43/* Scoping flags for lookup. */
 44#define LOOKUP_NO_SYMLINKS	BIT(24) /* No symlink crossing. */
 45#define LOOKUP_NO_MAGICLINKS	BIT(25) /* No nd_jump_link() crossing. */
 46#define LOOKUP_NO_XDEV		BIT(26) /* No mountpoint crossing. */
 47#define LOOKUP_BENEATH		BIT(27) /* No escaping from starting point. */
 48#define LOOKUP_IN_ROOT		BIT(28) /* Treat dirfd as fs root. */
 49/* LOOKUP_* flags which do scope-related checks based on the dirfd. */
 50#define LOOKUP_IS_SCOPED (LOOKUP_BENEATH | LOOKUP_IN_ROOT)
 51/* 3 spare bits for scoping */
 52
 53extern int path_pts(struct path *path);
 54
 55extern int user_path_at(int, const char __user *, unsigned, struct path *);
 56
 57struct dentry *lookup_one_qstr_excl(const struct qstr *name,
 58				    struct dentry *base,
 59				    unsigned int flags);
 60extern int kern_path(const char *, unsigned, struct path *);
 61struct dentry *kern_path_parent(const char *name, struct path *parent);
 62
 63extern struct dentry *start_creating_path(int, const char *, struct path *, unsigned int);
 64extern struct dentry *start_creating_user_path(int, const char __user *, struct path *, unsigned int);
 65extern void end_creating_path(const struct path *, struct dentry *);
 66extern struct dentry *start_removing_path(const char *, struct path *);
 67extern struct dentry *start_removing_user_path_at(int , const char __user *, struct path *);
 68static inline void end_removing_path(const struct path *path , struct dentry *dentry)
 69{
 70	end_creating_path(path, dentry);
 71}
 72int vfs_path_parent_lookup(struct filename *filename, unsigned int flags,
 73			   struct path *parent, struct qstr *last, int *type,
 74			   const struct path *root);
 75int vfs_path_lookup(struct dentry *, struct vfsmount *, const char *,
 76		    unsigned int, struct path *);
 77
 78extern struct dentry *try_lookup_noperm(struct qstr *, struct dentry *);
 79extern struct dentry *lookup_noperm(struct qstr *, struct dentry *);
 80extern struct dentry *lookup_noperm_unlocked(struct qstr *, struct dentry *);
 81extern struct dentry *lookup_noperm_positive_unlocked(struct qstr *, struct dentry *);
 82struct dentry *lookup_one(struct mnt_idmap *, struct qstr *, struct dentry *);
 83struct dentry *lookup_one_unlocked(struct mnt_idmap *idmap,
 84				   struct qstr *name, struct dentry *base);
 85struct dentry *lookup_one_positive_unlocked(struct mnt_idmap *idmap,
 86					    struct qstr *name,
 87					    struct dentry *base);
 88struct dentry *lookup_one_positive_killable(struct mnt_idmap *idmap,
 89					    struct qstr *name,
 90					    struct dentry *base);
 91
 92struct dentry *start_creating(struct mnt_idmap *idmap, struct dentry *parent,
 93			      struct qstr *name);
 94struct dentry *start_removing(struct mnt_idmap *idmap, struct dentry *parent,
 95			      struct qstr *name);
 96struct dentry *start_creating_killable(struct mnt_idmap *idmap,
 97				       struct dentry *parent,
 98				       struct qstr *name);
 99struct dentry *start_removing_killable(struct mnt_idmap *idmap,
100				       struct dentry *parent,
101				       struct qstr *name);
102struct dentry *start_creating_noperm(struct dentry *parent, struct qstr *name);
103struct dentry *start_removing_noperm(struct dentry *parent, struct qstr *name);
104struct dentry *start_creating_dentry(struct dentry *parent,
105				     struct dentry *child);
106struct dentry *start_removing_dentry(struct dentry *parent,
107				     struct dentry *child);
108
109/* end_creating - finish action started with start_creating
110 * @child: dentry returned by start_creating() or vfs_mkdir()
111 *
112 * Unlock and release the child. This can be called after
113 * start_creating() whether that function succeeded or not,
114 * but it is not needed on failure.
115 *
116 * If vfs_mkdir() was called then the value returned from that function
117 * should be given for @child rather than the original dentry, as vfs_mkdir()
118 * may have provided a new dentry.
119 *
120 *
121 * If vfs_mkdir() was not called, then @child will be a valid dentry and
122 * @parent will be ignored.
123 */
124static inline void end_creating(struct dentry *child)
125{
126	end_dirop(child);
127}
128
129/* end_creating_keep - finish action started with start_creating() and return result
130 * @child: dentry returned by start_creating() or vfs_mkdir()
131 *
132 * Unlock and return the child. This can be called after
133 * start_creating() whether that function succeeded or not,
134 * but it is not needed on failure.
135 *
136 * If vfs_mkdir() was called then the value returned from that function
137 * should be given for @child rather than the original dentry, as vfs_mkdir()
138 * may have provided a new dentry.
139 *
140 * Returns: @child, which may be a dentry or an error.
141 *
142 */
143static inline struct dentry *end_creating_keep(struct dentry *child)
144{
145	if (!IS_ERR(child))
146		dget(child);
147	end_dirop(child);
148	return child;
149}
150
151/**
152 * end_removing - finish action started with start_removing
153 * @child:  dentry returned by start_removing()
154 * @parent: dentry given to start_removing()
155 *
156 * Unlock and release the child.
157 *
158 * This is identical to end_dirop().  It can be passed the result of
159 * start_removing() whether that was successful or not, but it not needed
160 * if start_removing() failed.
161 */
162static inline void end_removing(struct dentry *child)
163{
164	end_dirop(child);
165}
166
167extern int follow_down_one(struct path *);
168extern int follow_down(struct path *path, unsigned int flags);
169extern int follow_up(struct path *);
170
171extern struct dentry *lock_rename(struct dentry *, struct dentry *);
172extern struct dentry *lock_rename_child(struct dentry *, struct dentry *);
173extern void unlock_rename(struct dentry *, struct dentry *);
174int start_renaming(struct renamedata *rd, int lookup_flags,
175		   struct qstr *old_last, struct qstr *new_last);
176int start_renaming_dentry(struct renamedata *rd, int lookup_flags,
177			  struct dentry *old_dentry, struct qstr *new_last);
178int start_renaming_two_dentries(struct renamedata *rd,
179				struct dentry *old_dentry, struct dentry *new_dentry);
180void end_renaming(struct renamedata *rd);
181
182/**
183 * mode_strip_umask - handle vfs umask stripping
184 * @dir:	parent directory of the new inode
185 * @mode:	mode of the new inode to be created in @dir
186 *
187 * In most filesystems, umask stripping depends on whether or not the
188 * filesystem supports POSIX ACLs. If the filesystem doesn't support it umask
189 * stripping is done directly in here. If the filesystem does support POSIX
190 * ACLs umask stripping is deferred until the filesystem calls
191 * posix_acl_create().
192 *
193 * Some filesystems (like NFSv4) also want to avoid umask stripping by the
194 * VFS, but don't support POSIX ACLs. Those filesystems can set SB_I_NOUMASK
195 * to get this effect without declaring that they support POSIX ACLs.
196 *
197 * Returns: mode
198 */
199static inline umode_t __must_check mode_strip_umask(const struct inode *dir, umode_t mode)
200{
201	if (!IS_POSIXACL(dir) && !(dir->i_sb->s_iflags & SB_I_NOUMASK))
202		mode &= ~current_umask();
203	return mode;
204}
205
206extern int __must_check nd_jump_link(const struct path *path);
207
208static inline void nd_terminate_link(void *name, size_t len, size_t maxlen)
209{
210	((char *) name)[min(len, maxlen)] = '\0';
211}
212
213/**
214 * retry_estale - determine whether the caller should retry an operation
215 * @error: the error that would currently be returned
216 * @flags: flags being used for next lookup attempt
217 *
218 * Check to see if the error code was -ESTALE, and then determine whether
219 * to retry the call based on whether "flags" already has LOOKUP_REVAL set.
220 *
221 * Returns true if the caller should try the operation again.
222 */
223static inline bool
224retry_estale(const long error, const unsigned int flags)
225{
226	return unlikely(error == -ESTALE && !(flags & LOOKUP_REVAL));
227}
228
229#endif /* _LINUX_NAMEI_H */