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 <mszeredi@suse.cz>
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index b7989f2..c3eb2c4 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -342,24 +342,6 @@
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 @@
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 @@
}
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 @@
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;