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Commit b70a80e7 authored by Miklos Szeredi's avatar Miklos Szeredi Committed by Al Viro
Browse files

vfs: introduce d_instantiate_no_diralias() 



...which just returns -EBUSY if a directory alias would be created.

This is to be used by fuse mkdir to make sure that a buggy or malicious
userspace filesystem doesn't do anything nasty.  Previously fuse used a
private mutex for this purpose, which can now go away.

Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
parent 94e92a6e

fs/dcache.c

+27 −0
Original line number Diff line number Diff line
@@ -1801,6 +1801,33 @@ struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode) 


EXPORT_SYMBOL(d_instantiate_unique);



/**

 * d_instantiate_no_diralias - instantiate a non-aliased dentry

 * @entry: dentry to complete

 * @inode: inode to attach to this dentry

 *

 * Fill in inode information in the entry.  If a directory alias is found, then

 * return an error (and drop inode).  Together with d_materialise_unique() this

 * guarantees that a directory inode may never have more than one alias.

 */

int d_instantiate_no_diralias(struct dentry *entry, struct inode *inode)

{

	BUG_ON(!hlist_unhashed(&entry->d_alias));



	spin_lock(&inode->i_lock);

	if (S_ISDIR(inode->i_mode) && !hlist_empty(&inode->i_dentry)) {

		spin_unlock(&inode->i_lock);

		iput(inode);

		return -EBUSY;

	}

	__d_instantiate(entry, inode);

	spin_unlock(&inode->i_lock);

	security_d_instantiate(entry, inode);



	return 0;

}

EXPORT_SYMBOL(d_instantiate_no_diralias);



struct dentry *d_make_root(struct inode *root_inode)

{

	struct dentry *res = NULL;

fs/fuse/dir.c

+5 −35
Original line number Diff line number Diff line
@@ -342,24 +342,6 @@ int fuse_lookup_name(struct super_block *sb, u64 nodeid, struct qstr *name, 
	return err;

}



static struct dentry *fuse_materialise_dentry(struct dentry *dentry,

					      struct inode *inode)

{

	struct dentry *newent;



	if (inode && S_ISDIR(inode->i_mode)) {

		struct fuse_conn *fc = get_fuse_conn(inode);



		mutex_lock(&fc->inst_mutex);

		newent = d_materialise_unique(dentry, inode);

		mutex_unlock(&fc->inst_mutex);

	} else {

		newent = d_materialise_unique(dentry, inode);

	}



	return newent;

}



static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,

				  unsigned int flags)

{
@@ -382,7 +364,7 @@ static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry, 
	if (inode && get_node_id(inode) == FUSE_ROOT_ID)

		goto out_iput;



	newent = fuse_materialise_dentry(entry, inode);

	newent = d_materialise_unique(entry, inode);

	err = PTR_ERR(newent);

	if (IS_ERR(newent))

		goto out_err;
@@ -601,21 +583,9 @@ static int create_new_entry(struct fuse_conn *fc, struct fuse_req *req, 
	}

	kfree(forget);



	if (S_ISDIR(inode->i_mode)) {

		struct dentry *alias;

		mutex_lock(&fc->inst_mutex);

		alias = d_find_alias(inode);

		if (alias) {

			/* New directory must have moved since mkdir */

			mutex_unlock(&fc->inst_mutex);

			dput(alias);

			iput(inode);

			return -EBUSY;

		}

		d_instantiate(entry, inode);

		mutex_unlock(&fc->inst_mutex);

	} else

		d_instantiate(entry, inode);

	err = d_instantiate_no_diralias(entry, inode);

	if (err)

		return err;



	fuse_change_entry_timeout(entry, &outarg);

	fuse_invalidate_attr(dir);
@@ -1284,7 +1254,7 @@ static int fuse_direntplus_link(struct file *file, 
	if (!inode)

		goto out;



	alias = fuse_materialise_dentry(dentry, inode);

	alias = d_materialise_unique(dentry, inode);

	err = PTR_ERR(alias);

	if (IS_ERR(alias))

		goto out;

fs/fuse/fuse_i.h

+0 −3
Original line number Diff line number Diff line
@@ -374,9 +374,6 @@ struct fuse_conn { 
	/** Lock protecting accessess to  members of this structure */

	spinlock_t lock;



	/** Mutex protecting against directory alias creation */

	struct mutex inst_mutex;



	/** Refcount */

	atomic_t count;

fs/fuse/inode.c

+0 −2
Original line number Diff line number Diff line
@@ -565,7 +565,6 @@ void fuse_conn_init(struct fuse_conn *fc) 
{

	memset(fc, 0, sizeof(*fc));

	spin_lock_init(&fc->lock);

	mutex_init(&fc->inst_mutex);

	init_rwsem(&fc->killsb);

	atomic_set(&fc->count, 1);

	init_waitqueue_head(&fc->waitq);
@@ -596,7 +595,6 @@ void fuse_conn_put(struct fuse_conn *fc) 
	if (atomic_dec_and_test(&fc->count)) {

		if (fc->destroy_req)

			fuse_request_free(fc->destroy_req);

		mutex_destroy(&fc->inst_mutex);

		fc->release(fc);

	}

}

include/linux/dcache.h

+1 −0
Original line number Diff line number Diff line
@@ -224,6 +224,7 @@ static inline int dname_external(const struct dentry *dentry) 
extern void d_instantiate(struct dentry *, struct inode *);

extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);

extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);

extern int d_instantiate_no_diralias(struct dentry *, struct inode *);

extern void __d_drop(struct dentry *dentry);

extern void d_drop(struct dentry *dentry);

extern void d_delete(struct dentry *);