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vfs: add cross-rename
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If flags contain RENAME_EXCHANGE then exchange source and destination files.
There's no restriction on the type of the files; e.g. a directory can be
exchanged with a symlink.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: J. Bruce Fields <bfields@redhat.com>
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Miklos Szeredi committed Apr 1, 2014
1 parent 4fd699a commit da1ce06
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Showing 5 changed files with 131 additions and 41 deletions.
50 changes: 41 additions & 9 deletions fs/dcache.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2483,12 +2483,14 @@ static void switch_names(struct dentry *dentry, struct dentry *target)
dentry->d_name.name = dentry->d_iname;
} else {
/*
* Both are internal. Just copy target to dentry
* Both are internal.
*/
memcpy(dentry->d_iname, target->d_name.name,
target->d_name.len + 1);
dentry->d_name.len = target->d_name.len;
return;
unsigned int i;
BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long)));
for (i = 0; i < DNAME_INLINE_LEN / sizeof(long); i++) {
swap(((long *) &dentry->d_iname)[i],
((long *) &target->d_iname)[i]);
}
}
}
swap(dentry->d_name.len, target->d_name.len);
Expand Down Expand Up @@ -2545,13 +2547,15 @@ static void dentry_unlock_parents_for_move(struct dentry *dentry,
* __d_move - move a dentry
* @dentry: entry to move
* @target: new dentry
* @exchange: exchange the two dentries
*
* Update the dcache to reflect the move of a file name. Negative
* dcache entries should not be moved in this way. Caller must hold
* rename_lock, the i_mutex of the source and target directories,
* and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
*/
static void __d_move(struct dentry * dentry, struct dentry * target)
static void __d_move(struct dentry *dentry, struct dentry *target,
bool exchange)
{
if (!dentry->d_inode)
printk(KERN_WARNING "VFS: moving negative dcache entry\n");
Expand All @@ -2573,8 +2577,15 @@ static void __d_move(struct dentry * dentry, struct dentry * target)
__d_drop(dentry);
__d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash));

/* Unhash the target: dput() will then get rid of it */
/*
* Unhash the target (d_delete() is not usable here). If exchanging
* the two dentries, then rehash onto the other's hash queue.
*/
__d_drop(target);
if (exchange) {
__d_rehash(target,
d_hash(dentry->d_parent, dentry->d_name.hash));
}

list_del(&dentry->d_u.d_child);
list_del(&target->d_u.d_child);
Expand All @@ -2601,6 +2612,8 @@ static void __d_move(struct dentry * dentry, struct dentry * target)
write_seqcount_end(&dentry->d_seq);

dentry_unlock_parents_for_move(dentry, target);
if (exchange)
fsnotify_d_move(target);
spin_unlock(&target->d_lock);
fsnotify_d_move(dentry);
spin_unlock(&dentry->d_lock);
Expand All @@ -2618,11 +2631,30 @@ static void __d_move(struct dentry * dentry, struct dentry * target)
void d_move(struct dentry *dentry, struct dentry *target)
{
write_seqlock(&rename_lock);
__d_move(dentry, target);
__d_move(dentry, target, false);
write_sequnlock(&rename_lock);
}
EXPORT_SYMBOL(d_move);

/*
* d_exchange - exchange two dentries
* @dentry1: first dentry
* @dentry2: second dentry
*/
void d_exchange(struct dentry *dentry1, struct dentry *dentry2)
{
write_seqlock(&rename_lock);

WARN_ON(!dentry1->d_inode);
WARN_ON(!dentry2->d_inode);
WARN_ON(IS_ROOT(dentry1));
WARN_ON(IS_ROOT(dentry2));

__d_move(dentry1, dentry2, true);

write_sequnlock(&rename_lock);
}

/**
* d_ancestor - search for an ancestor
* @p1: ancestor dentry
Expand Down Expand Up @@ -2670,7 +2702,7 @@ static struct dentry *__d_unalias(struct inode *inode,
m2 = &alias->d_parent->d_inode->i_mutex;
out_unalias:
if (likely(!d_mountpoint(alias))) {
__d_move(alias, dentry);
__d_move(alias, dentry, false);
ret = alias;
}
out_err:
Expand Down
104 changes: 72 additions & 32 deletions fs/namei.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4031,6 +4031,8 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
const unsigned char *old_name;
struct inode *source = old_dentry->d_inode;
struct inode *target = new_dentry->d_inode;
bool new_is_dir = false;
unsigned max_links = new_dir->i_sb->s_max_links;

if (source == target)
return 0;
Expand All @@ -4039,10 +4041,16 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
if (error)
return error;

if (!target)
if (!target) {
error = may_create(new_dir, new_dentry);
else
error = may_delete(new_dir, new_dentry, is_dir);
} else {
new_is_dir = d_is_dir(new_dentry);

if (!(flags & RENAME_EXCHANGE))
error = may_delete(new_dir, new_dentry, is_dir);
else
error = may_delete(new_dir, new_dentry, new_is_dir);
}
if (error)
return error;

Expand All @@ -4056,10 +4064,17 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
* If we are going to change the parent - check write permissions,
* we'll need to flip '..'.
*/
if (is_dir && new_dir != old_dir) {
error = inode_permission(source, MAY_WRITE);
if (error)
return error;
if (new_dir != old_dir) {
if (is_dir) {
error = inode_permission(source, MAY_WRITE);
if (error)
return error;
}
if ((flags & RENAME_EXCHANGE) && new_is_dir) {
error = inode_permission(target, MAY_WRITE);
if (error)
return error;
}
}

error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry,
Expand All @@ -4069,7 +4084,7 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,

old_name = fsnotify_oldname_init(old_dentry->d_name.name);
dget(new_dentry);
if (!is_dir)
if (!is_dir || (flags & RENAME_EXCHANGE))
lock_two_nondirectories(source, target);
else if (target)
mutex_lock(&target->i_mutex);
Expand All @@ -4078,25 +4093,25 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
if (d_mountpoint(old_dentry) || d_mountpoint(new_dentry))
goto out;

if (is_dir) {
unsigned max_links = new_dir->i_sb->s_max_links;

if (max_links && new_dir != old_dir) {
error = -EMLINK;
if (max_links && !target && new_dir != old_dir &&
new_dir->i_nlink >= max_links)
if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links)
goto out;

if (target)
shrink_dcache_parent(new_dentry);
} else {
if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir &&
old_dir->i_nlink >= max_links)
goto out;
}
if (is_dir && !(flags & RENAME_EXCHANGE) && target)
shrink_dcache_parent(new_dentry);
if (!is_dir) {
error = try_break_deleg(source, delegated_inode);
if (error)
goto out;
if (target) {
error = try_break_deleg(target, delegated_inode);
if (error)
goto out;
}
}
if (target && !new_is_dir) {
error = try_break_deleg(target, delegated_inode);
if (error)
goto out;
}
if (!flags) {
error = old_dir->i_op->rename(old_dir, old_dentry,
Expand All @@ -4108,22 +4123,31 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
if (error)
goto out;

if (target) {
if (!(flags & RENAME_EXCHANGE) && target) {
if (is_dir)
target->i_flags |= S_DEAD;
dont_mount(new_dentry);
}
if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
d_move(old_dentry, new_dentry);
if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) {
if (!(flags & RENAME_EXCHANGE))
d_move(old_dentry, new_dentry);
else
d_exchange(old_dentry, new_dentry);
}
out:
if (!is_dir)
if (!is_dir || (flags & RENAME_EXCHANGE))
unlock_two_nondirectories(source, target);
else if (target)
mutex_unlock(&target->i_mutex);
dput(new_dentry);
if (!error)
if (!error) {
fsnotify_move(old_dir, new_dir, old_name, is_dir,
target, old_dentry);
!(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry);
if (flags & RENAME_EXCHANGE) {
fsnotify_move(new_dir, old_dir, old_dentry->d_name.name,
new_is_dir, NULL, new_dentry);
}
}
fsnotify_oldname_free(old_name);

return error;
Expand All @@ -4143,7 +4167,10 @@ SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname,
bool should_retry = false;
int error;

if (flags & ~RENAME_NOREPLACE)
if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
return -EINVAL;

if ((flags & RENAME_NOREPLACE) && (flags & RENAME_EXCHANGE))
return -EINVAL;

retry:
Expand Down Expand Up @@ -4180,7 +4207,8 @@ SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname,

oldnd.flags &= ~LOOKUP_PARENT;
newnd.flags &= ~LOOKUP_PARENT;
newnd.flags |= LOOKUP_RENAME_TARGET;
if (!(flags & RENAME_EXCHANGE))
newnd.flags |= LOOKUP_RENAME_TARGET;

retry_deleg:
trap = lock_rename(new_dir, old_dir);
Expand All @@ -4200,20 +4228,32 @@ SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname,
error = -EEXIST;
if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry))
goto exit5;
if (flags & RENAME_EXCHANGE) {
error = -ENOENT;
if (d_is_negative(new_dentry))
goto exit5;

if (!d_is_dir(new_dentry)) {
error = -ENOTDIR;
if (newnd.last.name[newnd.last.len])
goto exit5;
}
}
/* unless the source is a directory trailing slashes give -ENOTDIR */
if (!d_is_dir(old_dentry)) {
error = -ENOTDIR;
if (oldnd.last.name[oldnd.last.len])
goto exit5;
if (newnd.last.name[newnd.last.len])
if (!(flags & RENAME_EXCHANGE) && newnd.last.name[newnd.last.len])
goto exit5;
}
/* source should not be ancestor of target */
error = -EINVAL;
if (old_dentry == trap)
goto exit5;
/* target should not be an ancestor of source */
error = -ENOTEMPTY;
if (!(flags & RENAME_EXCHANGE))
error = -ENOTEMPTY;
if (new_dentry == trap)
goto exit5;

Expand Down
1 change: 1 addition & 0 deletions include/linux/dcache.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -308,6 +308,7 @@ extern void dentry_update_name_case(struct dentry *, struct qstr *);

/* used for rename() and baskets */
extern void d_move(struct dentry *, struct dentry *);
extern void d_exchange(struct dentry *, struct dentry *);
extern struct dentry *d_ancestor(struct dentry *, struct dentry *);

/* appendix may either be NULL or be used for transname suffixes */
Expand Down
1 change: 1 addition & 0 deletions include/uapi/linux/fs.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,7 @@
#define SEEK_MAX SEEK_HOLE

#define RENAME_NOREPLACE (1 << 0) /* Don't overwrite target */
#define RENAME_EXCHANGE (1 << 1) /* Exchange source and dest */

struct fstrim_range {
__u64 start;
Expand Down
16 changes: 16 additions & 0 deletions security/security.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -439,6 +439,14 @@ int security_path_rename(struct path *old_dir, struct dentry *old_dentry,
if (unlikely(IS_PRIVATE(old_dentry->d_inode) ||
(new_dentry->d_inode && IS_PRIVATE(new_dentry->d_inode))))
return 0;

if (flags & RENAME_EXCHANGE) {
int err = security_ops->path_rename(new_dir, new_dentry,
old_dir, old_dentry);
if (err)
return err;
}

return security_ops->path_rename(old_dir, old_dentry, new_dir,
new_dentry);
}
Expand Down Expand Up @@ -531,6 +539,14 @@ int security_inode_rename(struct inode *old_dir, struct dentry *old_dentry,
if (unlikely(IS_PRIVATE(old_dentry->d_inode) ||
(new_dentry->d_inode && IS_PRIVATE(new_dentry->d_inode))))
return 0;

if (flags & RENAME_EXCHANGE) {
int err = security_ops->inode_rename(new_dir, new_dentry,
old_dir, old_dentry);
if (err)
return err;
}

return security_ops->inode_rename(old_dir, old_dentry,
new_dir, new_dentry);
}
Expand Down

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