On Wed, Nov 20, 2013 at 5:01 AM, Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
> 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.
What happens if both RENAME_EXCHANGE and RENAME_NOREPLACE are set?
--Andy
>
> Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
> ---
> fs/dcache.c | 46 +++++++++++++++++----
> fs/namei.c | 107 +++++++++++++++++++++++++++++++++---------------
> include/linux/dcache.h | 1 +
> include/uapi/linux/fs.h | 1 +
> security/security.c | 16 ++++++++
> 5 files changed, 131 insertions(+), 40 deletions(-)
>
> diff --git a/fs/dcache.c b/fs/dcache.c
> index 0a38ef8d7f00..ea2fca1a2ec9 100644
> --- a/fs/dcache.c
> +++ b/fs/dcache.c
> @@ -2527,12 +2527,14 @@ 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);
> @@ -2589,13 +2591,15 @@ 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");
> @@ -2619,6 +2623,10 @@ 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);
> @@ -2645,6 +2653,8 @@ 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);
> @@ -2662,11 +2672,31 @@ 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
> @@ -2714,7 +2744,7 @@ 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 5b41d4bfecd1..c23621255df0 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -4025,6 +4025,8 @@ 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;
> @@ -4033,10 +4035,16 @@ 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;
>
> @@ -4047,10 +4055,17 @@ 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,
> @@ -4060,25 +4075,24 @@ 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)
> - lock_two_nondirectories(source, target);
> - else if (target)
> - mutex_lock(&target->i_mutex);
> + if (!(flags & RENAME_EXCHANGE)) {
> + if (!is_dir)
> + lock_two_nondirectories(source, target);
> + else if (target)
> + mutex_lock(&target->i_mutex);
> + }
>
> error = -EBUSY;
> 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 ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir &&
> + old_dir->i_nlink > max_links)
> goto out;
> -
> - if (target)
> - shrink_dcache_parent(new_dentry);
> } else {
> error = try_break_deleg(source, delegated_inode);
> if (error)
> @@ -4089,27 +4103,40 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
> goto out;
> }
> }
> + if (is_dir && !(flags & RENAME_EXCHANGE) && target)
> + shrink_dcache_parent(new_dentry);
> error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry,
> flags);
> 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)
> - unlock_two_nondirectories(source, target);
> - else if (target)
> - mutex_unlock(&target->i_mutex);
> + if (!(flags & RENAME_EXCHANGE)) {
> + if (!is_dir)
> + 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;
> @@ -4129,9 +4156,12 @@ 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 -EOPNOTSUPP;
>
> + if ((flags & RENAME_NOREPLACE) && (flags & RENAME_EXCHANGE))
> + return -EINVAL;
> +
> retry:
> from = user_path_parent(olddfd, oldname, &oldnd, lookup_flags);
> if (IS_ERR(from)) {
> @@ -4166,7 +4196,8 @@ 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);
> @@ -4186,12 +4217,23 @@ retry_deleg:
> error = -EEXIST;
> if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry))
> goto exit5;
> + if (flags & RENAME_EXCHANGE) {
> + error = -ENOENT;
> + if (!new_dentry->d_inode)
> + 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 */
> @@ -4199,7 +4241,8 @@ 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 901616910e0a..87e14e698f89 100644
> --- a/include/linux/dcache.h
> +++ b/include/linux/dcache.h
> @@ -306,6 +306,7 @@ 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 d00ae28dea76..0ef72cd2255f 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
>
--
Andy Lutomirski
AMA Capital Management, LLC
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