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

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On 14/11/2022 19:24, Jeff Layton wrote:
On Mon, 2022-11-14 at 13:19 +0800, xiubli@xxxxxxxxxx wrote:
From: Xiubo Li <xiubli@xxxxxxxxxx>

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@xxxxxxxxxxxxxxx
URL: https://tracker.ceph.com/issues/57986
Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx>
---
  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?

Yeah, I didn't fix this in the this patch. I fixed it in a dedicated 2/2 patch.

  I think you may need to get rid of
the "num_locks" field in ceph_file_info, and do that in a different way?

This is a dedicated field for each 'file' struct. I have no idea how to fix this in a different way yet.

Thanks!

- Xiubo


  }
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;




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