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Simplifying ->d_name audits, easy part. 

Turn dentry->d_name into an anon union of const struct qsrt (d_name
 itself) and a writable alias (__d_name).  With constification of some
 struct qstr * arguments of functions that get &dentry->d_name passed
 to them, that ends up with all modifications provably done only in
 fs/dcache.c (and a fairly small part of it).
 
 Any new places doing modifications will be easy to find - grep for
 __d_name will suffice.
 
 Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Merge tag 'pull-qstr' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull d_name audit update from Al Viro:
 "Simplifying ->d_name audits, easy part.

  Turn dentry->d_name into an anon union of const struct qsrt (d_name
  itself) and a writable alias (__d_name).

  With constification of some struct qstr * arguments of functions that
  get &dentry->d_name passed to them, that ends up with all
  modifications provably done only in fs/dcache.c (and a fairly small
  part of it).

  Any new places doing modifications will be easy to find - grep for
  __d_name will suffice"

* tag 'pull-qstr' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  make it easier to catch those who try to modify ->d_name
  generic_ci_validate_strict_name(): constify name argument
  afs_dir_search: constify qstr argument
  afs_edit_dir_{add,remove}(): constify qstr argument
  exfat_find(): constify qstr argument
  security_dentry_init_security(): constify qstr argument
This commit is contained in:
Linus Torvalds 2025-10-03 11:14:02 -07:00
parent 829745b75a 180a9cc3fd
commit 33fc69a05c
12 changed files with 34 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
fs/afs/dir_edit.c
View File

@ -239,7 +239,7 @@ static void afs_edit_init_block(union afs_xdr_dir_block *meta,
* The caller must hold the inode locked.
*/
void afs_edit_dir_add(struct afs_vnode *vnode,
struct qstr *name, struct afs_fid *new_fid,
const struct qstr *name, struct afs_fid *new_fid,
enum afs_edit_dir_reason why)
{
union afs_xdr_dir_block *meta, *block;
@ -391,7 +391,7 @@ error:
* The caller must hold the inode locked.
*/
void afs_edit_dir_remove(struct afs_vnode *vnode,
struct qstr *name, enum afs_edit_dir_reason why)
const struct qstr *name, enum afs_edit_dir_reason why)
{
union afs_xdr_dir_block *meta, *block, *pblock;
union afs_xdr_dirent *de, *pde;

2
fs/afs/dir_search.c
View File

@ -188,7 +188,7 @@ bad:
/*
* Search the appropriate hash chain in the contents of an AFS directory.
*/
int afs_dir_search(struct afs_vnode *dvnode, struct qstr *name,
int afs_dir_search(struct afs_vnode *dvnode, const struct qstr *name,
struct afs_fid *_fid, afs_dataversion_t *_dir_version)
{
struct afs_dir_iter iter = { .dvnode = dvnode, };

6
fs/afs/internal.h
View File

@ -1099,9 +1099,9 @@ int afs_single_writepages(struct address_space *mapping,
/*
* dir_edit.c
*/
extern void afs_edit_dir_add(struct afs_vnode *, struct qstr *, struct afs_fid *,
extern void afs_edit_dir_add(struct afs_vnode *, const struct qstr *, struct afs_fid *,
enum afs_edit_dir_reason);
extern void afs_edit_dir_remove(struct afs_vnode *, struct qstr *, enum afs_edit_dir_reason);
extern void afs_edit_dir_remove(struct afs_vnode *, const struct qstr *, enum afs_edit_dir_reason);
void afs_edit_dir_update(struct afs_vnode *vnode, const struct qstr *name,
struct afs_vnode *new_dvnode, enum afs_edit_dir_reason why);
void afs_mkdir_init_dir(struct afs_vnode *dvnode, struct afs_vnode *parent_vnode);
@ -1114,7 +1114,7 @@ bool afs_dir_init_iter(struct afs_dir_iter *iter, const struct qstr *name);
union afs_xdr_dir_block *afs_dir_find_block(struct afs_dir_iter *iter, size_t block);
int afs_dir_search_bucket(struct afs_dir_iter *iter, const struct qstr *name,
struct afs_fid *_fid);
int afs_dir_search(struct afs_vnode *dvnode, struct qstr *name,
int afs_dir_search(struct afs_vnode *dvnode, const struct qstr *name,
struct afs_fid *_fid, afs_dataversion_t *_dir_version);
/*

26
fs/dcache.c
View File

@ -1717,13 +1717,13 @@ static struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
dname = dentry->d_shortname.string;
}
dentry->d_name.len = name->len;
dentry->d_name.hash = name->hash;
dentry->__d_name.len = name->len;
dentry->__d_name.hash = name->hash;
memcpy(dname, name->name, name->len);
dname[name->len] = 0;
/* Make sure we always see the terminating NUL character */
smp_store_release(&dentry->d_name.name, dname); /* ^^^ */
smp_store_release(&dentry->__d_name.name, dname); /* ^^^ */
dentry->d_flags = 0;
lockref_init(&dentry->d_lockref);
@ -2743,15 +2743,15 @@ static void swap_names(struct dentry *dentry, struct dentry *target)
/*
* Both external: swap the pointers
*/
swap(target->d_name.name, dentry->d_name.name);
swap(target->__d_name.name, dentry->__d_name.name);
} else {
/*
* dentry:internal, target:external. Steal target's
* storage and make target internal.
*/
dentry->d_name.name = target->d_name.name;
dentry->__d_name.name = target->__d_name.name;
target->d_shortname = dentry->d_shortname;
target->d_name.name = target->d_shortname.string;
target->__d_name.name = target->d_shortname.string;
}
} else {
if (unlikely(dname_external(dentry))) {
@ -2759,9 +2759,9 @@ static void swap_names(struct dentry *dentry, struct dentry *target)
* dentry:external, target:internal. Give dentry's
* storage to target and make dentry internal
*/
target->d_name.name = dentry->d_name.name;
target->__d_name.name = dentry->__d_name.name;
dentry->d_shortname = target->d_shortname;
dentry->d_name.name = dentry->d_shortname.string;
dentry->__d_name.name = dentry->d_shortname.string;
} else {
/*
* Both are internal.
@ -2771,7 +2771,7 @@ static void swap_names(struct dentry *dentry, struct dentry *target)
target->d_shortname.words[i]);
}
}
swap(dentry->d_name.hash_len, target->d_name.hash_len);
swap(dentry->__d_name.hash_len, target->__d_name.hash_len);
}
static void copy_name(struct dentry *dentry, struct dentry *target)
@ -2781,11 +2781,11 @@ static void copy_name(struct dentry *dentry, struct dentry *target)
old_name = external_name(dentry);
if (unlikely(dname_external(target))) {
atomic_inc(&external_name(target)->count);
dentry->d_name = target->d_name;
dentry->__d_name = target->__d_name;
} else {
dentry->d_shortname = target->d_shortname;
dentry->d_name.name = dentry->d_shortname.string;
dentry->d_name.hash_len = target->d_name.hash_len;
dentry->__d_name.name = dentry->d_shortname.string;
dentry->__d_name.hash_len = target->__d_name.hash_len;
}
if (old_name && likely(atomic_dec_and_test(&old_name->count)))
kfree_rcu(old_name, head);
@ -3134,7 +3134,7 @@ void d_mark_tmpfile(struct file *file, struct inode *inode)
!d_unlinked(dentry));
spin_lock(&dentry->d_parent->d_lock);
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
dentry->d_name.len = sprintf(dentry->d_shortname.string, "#%llu",
dentry->__d_name.len = sprintf(dentry->d_shortname.string, "#%llu",
(unsigned long long)inode->i_ino);
spin_unlock(&dentry->d_lock);
spin_unlock(&dentry->d_parent->d_lock);

2
fs/exfat/namei.c
View File

@ -587,7 +587,7 @@ unlock:
}
/* lookup a file */
static int exfat_find(struct inode *dir, struct qstr *qname,
static int exfat_find(struct inode *dir, const struct qstr *qname,
struct exfat_dir_entry *info)
{
int ret, dentry, count;

5
include/linux/dcache.h
View File

@ -95,7 +95,10 @@ struct dentry {
seqcount_spinlock_t d_seq; /* per dentry seqlock */
struct hlist_bl_node d_hash; /* lookup hash list */
struct dentry *d_parent; /* parent directory */
struct qstr d_name;
union {
struct qstr __d_name; /* for use ONLY in fs/dcache.c */
const struct qstr d_name;
};
struct inode *d_inode; /* Where the name belongs to - NULL is
* negative */
union shortname_store d_shortname;

6
include/linux/fs.h
View File

@ -3716,7 +3716,8 @@ int generic_ci_d_compare(const struct dentry *dentry, unsigned int len,
* happens when a directory is casefolded and the filesystem is strict
* about its encoding.
*/
static inline bool generic_ci_validate_strict_name(struct inode *dir, struct qstr *name)
static inline bool generic_ci_validate_strict_name(struct inode *dir,
const struct qstr *name)
{
if (!IS_CASEFOLDED(dir) || !sb_has_strict_encoding(dir->i_sb))
return true;
@ -3731,7 +3732,8 @@ static inline bool generic_ci_validate_strict_name(struct inode *dir, struct qst
return !utf8_validate(dir->i_sb->s_encoding, name);
}
#else
static inline bool generic_ci_validate_strict_name(struct inode *dir, struct qstr *name)
static inline bool generic_ci_validate_strict_name(struct inode *dir,
const struct qstr *name)
{
return true;
}

2
include/linux/lsm_hook_defs.h
View File

@ -85,7 +85,7 @@ LSM_HOOK(int, -EOPNOTSUPP, dentry_init_security, struct dentry *dentry,
int mode, const struct qstr *name, const char **xattr_name,
struct lsm_context *cp)
LSM_HOOK(int, 0, dentry_create_files_as, struct dentry *dentry, int mode,
struct qstr *name, const struct cred *old, struct cred *new)
const struct qstr *name, const struct cred *old, struct cred *new)
#ifdef CONFIG_SECURITY_PATH
LSM_HOOK(int, 0, path_unlink, const struct path *dir, struct dentry *dentry)

4
include/linux/security.h
View File

@ -391,7 +391,7 @@ int security_dentry_init_security(struct dentry *dentry, int mode,
const char **xattr_name,
struct lsm_context *lsmcxt);
int security_dentry_create_files_as(struct dentry *dentry, int mode,
struct qstr *name,
const struct qstr *name,
const struct cred *old,
struct cred *new);
int security_path_notify(const struct path *path, u64 mask,
@ -872,7 +872,7 @@ static inline int security_dentry_init_security(struct dentry *dentry,
}
static inline int security_dentry_create_files_as(struct dentry *dentry,
int mode, struct qstr *name,
int mode, const struct qstr *name,
const struct cred *old,
struct cred *new)
{

2
security/security.c
View File

@ -1814,7 +1814,7 @@ EXPORT_SYMBOL(security_dentry_init_security);
* Return: Returns 0 on success, error on failure.
*/
int security_dentry_create_files_as(struct dentry *dentry, int mode,
struct qstr *name,
const struct qstr *name,
const struct cred *old, struct cred *new)
{
return call_int_hook(dentry_create_files_as, dentry, mode,

2
security/selinux/hooks.c
View File

@ -2905,7 +2905,7 @@ static int selinux_dentry_init_security(struct dentry *dentry, int mode,
}
static int selinux_dentry_create_files_as(struct dentry *dentry, int mode,
struct qstr *name,
const struct qstr *name,
const struct cred *old,
struct cred *new)
{

2
security/smack/smack_lsm.c
View File

@ -4908,7 +4908,7 @@ static int smack_inode_copy_up_xattr(struct dentry *src, const char *name)
}
static int smack_dentry_create_files_as(struct dentry *dentry, int mode,
struct qstr *name,
const struct qstr *name,
const struct cred *old,
struct cred *new)
{