From c9ba789dad15ba65662bba17595c0aeaa0cfcf1c Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Thu, 13 Nov 2025 11:18:29 +1100 Subject: VFS: introduce start_creating_noperm() and start_removing_noperm() xfs, fuse, ipc/mqueue need variants of start_creating or start_removing which do not check permissions. This patch adds _noperm versions of these functions. Note that do_mq_open() was only calling mntget() so it could call path_put() - it didn't really need an extra reference on the mnt. Now it doesn't call mntget() and uses end_creating() which does the dput() half of path_put(). Also mq_unlink() previously passed d_inode(dentry->d_parent) as the dir inode to vfs_unlink(). This is after locking d_inode(mnt->mnt_root) These two inodes are the same, but normally calls use the textual parent. So I've changes the vfs_unlink() call to be given d_inode(mnt->mnt_root). Reviewed-by: Amir Goldstein Reviewed-by: Jeff Layton Signed-off-by: NeilBrown -- changes since v2: - dir arg passed to vfs_unlink() in mq_unlink() changed to match the dir passed to lookup_noperm() - restore assignment to path->mnt even though the mntget() is removed. Link: https://patch.msgid.link/20251113002050.676694-7-neilb@ownmail.net Tested-by: syzbot@syzkaller.appspotmail.com Signed-off-by: Christian Brauner --- fs/fuse/dir.c | 19 ++++++++----------- 1 file changed, 8 insertions(+), 11 deletions(-) (limited to 'fs/fuse') diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index ecaec0fea3a1..40ca94922349 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -1397,27 +1397,25 @@ int fuse_reverse_inval_entry(struct fuse_conn *fc, u64 parent_nodeid, if (!parent) return -ENOENT; - inode_lock_nested(parent, I_MUTEX_PARENT); if (!S_ISDIR(parent->i_mode)) - goto unlock; + goto put_parent; err = -ENOENT; dir = d_find_alias(parent); if (!dir) - goto unlock; + goto put_parent; - name->hash = full_name_hash(dir, name->name, name->len); - entry = d_lookup(dir, name); + entry = start_removing_noperm(dir, name); dput(dir); - if (!entry) - goto unlock; + if (IS_ERR(entry)) + goto put_parent; fuse_dir_changed(parent); if (!(flags & FUSE_EXPIRE_ONLY)) d_invalidate(entry); fuse_invalidate_entry_cache(entry); - if (child_nodeid != 0 && d_really_is_positive(entry)) { + if (child_nodeid != 0) { inode_lock(d_inode(entry)); if (get_node_id(d_inode(entry)) != child_nodeid) { err = -ENOENT; @@ -1445,10 +1443,9 @@ int fuse_reverse_inval_entry(struct fuse_conn *fc, u64 parent_nodeid, } else { err = 0; } - dput(entry); - unlock: - inode_unlock(parent); + end_removing(entry); + put_parent: iput(parent); return err; } -- cgit v1.2.3