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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 <amir73il@gmail.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> Signed-off-by: NeilBrown <neil@brown.name> -- 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 <brauner@kernel.org>