Re: [PATCH 1/2 v2] ceph: add ceph_lock_info support for file_lock

[Jeff Layton <jlayton@kernel.org>]

On Mon, 2022-11-14 at 13:19 +0800, xiubli@redhat.com wrote:
> From: Xiubo Li <xiubli@redhat.com>
> 
> When ceph releasing the file_lock it will try to get the inode pointer
> from the fl->fl_file, which the memory could already be released by
> another thread in filp_close(). Because in VFS layer the fl->fl_file
> doesn't increase the file's reference counter.
> 
> Will switch to use ceph dedicate lock info to track the inode.
> 
> And in ceph_fl_release_lock() we should skip all the operations if
> the fl->fl_u.ceph_fl.fl_inode is not set, which should come from
> the request file_lock. And we will set fl->fl_u.ceph_fl.fl_inode when
> inserting it to the inode lock list, which is when copying the lock.
> 
> Cc: stable@vger.kernel.org
> URL: https://tracker.ceph.com/issues/57986
> Signed-off-by: Xiubo Li <xiubli@redhat.com>
> ---
>  fs/ceph/locks.c                 | 18 +++++++++++++++---
>  include/linux/ceph/ceph_fs_fl.h | 26 ++++++++++++++++++++++++++
>  include/linux/fs.h              |  2 ++
>  3 files changed, 43 insertions(+), 3 deletions(-)
>  create mode 100644 include/linux/ceph/ceph_fs_fl.h
> 
> diff --git a/fs/ceph/locks.c b/fs/ceph/locks.c
> index 3e2843e86e27..d8385dd0076e 100644
> --- a/fs/ceph/locks.c
> +++ b/fs/ceph/locks.c
> @@ -34,22 +34,34 @@ static void ceph_fl_copy_lock(struct file_lock *dst, struct file_lock *src)
>  {
>  	struct ceph_file_info *fi = dst->fl_file->private_data;
>  	struct inode *inode = file_inode(dst->fl_file);
> +
>  	atomic_inc(&ceph_inode(inode)->i_filelock_ref);
>  	atomic_inc(&fi->num_locks);
> +	dst->fl_u.ceph_fl.fl_inode = igrab(inode);
>  }
>  
>  static void ceph_fl_release_lock(struct file_lock *fl)
>  {
>  	struct ceph_file_info *fi = fl->fl_file->private_data;
> -	struct inode *inode = file_inode(fl->fl_file);
> -	struct ceph_inode_info *ci = ceph_inode(inode);
> -	atomic_dec(&fi->num_locks);
> +	struct inode *inode = fl->fl_u.ceph_fl.fl_inode;
> +	struct ceph_inode_info *ci;
> +
> +	/*
> +	 * If inode is NULL it should be a request file_lock,
> +	 * nothing we can do.
> +	 */
> +	if (!inode)
> +		return;
> +
> +	ci = ceph_inode(inode);
>  	if (atomic_dec_and_test(&ci->i_filelock_ref)) {
>  		/* clear error when all locks are released */
>  		spin_lock(&ci->i_ceph_lock);
>  		ci->i_ceph_flags &= ~CEPH_I_ERROR_FILELOCK;
>  		spin_unlock(&ci->i_ceph_lock);
>  	}
> +	iput(inode);
> +	atomic_dec(&fi->num_locks);

It doesn't look like this fixes the original issue. "fi" may be pointing
to freed memory at this point, right? I think you may need to get rid of
the "num_locks" field in ceph_file_info, and do that in a different way?

>  }
>  
>  static const struct file_lock_operations ceph_fl_lock_ops = {
> diff --git a/include/linux/ceph/ceph_fs_fl.h b/include/linux/ceph/ceph_fs_fl.h
> new file mode 100644
> index 000000000000..02a412b26095
> --- /dev/null
> +++ b/include/linux/ceph/ceph_fs_fl.h
> @@ -0,0 +1,26 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * ceph_fs.h - Ceph constants and data types to share between kernel and
> + * user space.
> + *
> + * Most types in this file are defined as little-endian, and are
> + * primarily intended to describe data structures that pass over the
> + * wire or that are stored on disk.
> + *
> + * LGPL2
> + */
> +
> +#ifndef CEPH_FS_FL_H
> +#define CEPH_FS_FL_H
> +
> +#include <linux/fs.h>
> +
> +/*
> + * Ceph lock info
> + */
> +
> +struct ceph_lock_info {
> +	struct inode *fl_inode;
> +};
> +
> +#endif
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index e654435f1651..db4810d19e26 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1066,6 +1066,7 @@ bool opens_in_grace(struct net *);
>  
>  /* that will die - we need it for nfs_lock_info */
>  #include <linux/nfs_fs_i.h>
> +#include <linux/ceph/ceph_fs_fl.h>
>  
>  /*
>   * struct file_lock represents a generic "file lock". It's used to represent
> @@ -1119,6 +1120,7 @@ struct file_lock {
>  			int state;		/* state of grant or error if -ve */
>  			unsigned int	debug_id;
>  		} afs;
> +		struct ceph_lock_info	ceph_fl;
>  	} fl_u;
>  } __randomize_layout;
>  

-- 
Jeff Layton <jlayton@kernel.org>