[PATCH 08/13] vfs: add cross-rename
From: Miklos Szeredi
Date: Fri Feb 07 2014 - 11:54:16 EST
From: Miklos Szeredi <mszeredi@xxxxxxx>
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@xxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
---
fs/dcache.c | 45 +++++++++++++++++----
fs/namei.c | 104 +++++++++++++++++++++++++++++++++---------------
include/linux/dcache.h | 1 +
include/uapi/linux/fs.h | 1 +
security/security.c | 16 ++++++++
5 files changed, 127 insertions(+), 40 deletions(-)
diff --git a/fs/dcache.c b/fs/dcache.c
index 265e0ce9769c..bd6f96497402 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -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);
@@ -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");
@@ -2575,6 +2579,10 @@ static void __d_move(struct dentry * dentry, struct dentry * target)
/* Unhash the target: dput() will then get rid of it */
__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);
@@ -2601,6 +2609,8 @@ 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);
@@ -2618,11 +2628,30 @@ 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
@@ -2670,7 +2699,7 @@ 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:
diff --git a/fs/namei.c b/fs/namei.c
index 1974a07835f7..50b0ca3dddc3 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -4004,6 +4004,8 @@ 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;
@@ -4012,10 +4014,16 @@ 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;
@@ -4029,10 +4037,17 @@ 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,
@@ -4042,7 +4057,7 @@ 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);
@@ -4051,25 +4066,25 @@ 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,
@@ -4081,22 +4096,31 @@ 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;
@@ -4116,7 +4140,10 @@ 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:
@@ -4153,7 +4180,8 @@ retry:
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);
@@ -4173,12 +4201,23 @@ retry_deleg:
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 */
@@ -4186,7 +4225,8 @@ retry_deleg:
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;
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 3b50cac7ccb3..3b9bfdb83ba6 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -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 */
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index 9250f4dd7d96..ca1a11bb4443 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -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;
diff --git a/security/security.c b/security/security.c
index edc179f1ade0..3dd2258b7a38 100644
--- a/security/security.c
+++ b/security/security.c
@@ -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);
}
@@ -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);
}
--
1.8.1.4
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