From: Miklos Szeredi Date: Tue, 1 Oct 2013 14:44:54 +0000 (+0200) Subject: vfs: introduce d_instantiate_no_diralias() X-Git-Tag: next-20131017~85^2~4 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=9b256c19ebdee35ac9daaf6d18993bb5e338ade5;p=karo-tx-linux.git 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: Miklos Szeredi --- diff --git a/fs/dcache.c b/fs/dcache.c index 41000305d716..59c06e5b3c27 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -1801,6 +1801,32 @@ 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. 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); + 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; diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index b7989f2ab4c4..0747f6eed598 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -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 +583,11 @@ 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) { + iput(inode); + return err; + } fuse_change_entry_timeout(entry, &outarg); fuse_invalidate_attr(dir); @@ -1284,7 +1256,7 @@ 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; diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h index 643274852c8b..71eb9d987757 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -375,9 +375,6 @@ 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; diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index a8ce6dab60a0..1c15613c64f8 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -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); } } diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 59066e0b4ff1..716c3760ee39 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -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 *);