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Revision 88956eabfdea7d01d550535af120d4ef265b1d02 authored by NeilBrown on 12 September 2023, 01:25:00 UTC, committed by Chuck Lever on 12 September 2023, 13:39:35 UTC 
NFSD: fix possible oops when nfsd/pool_stats is closed.
 
If /proc/fs/nfsd/pool_stats is open when the last nfsd thread exits, then
when the file is closed a NULL pointer is dereferenced.
This is because nfsd_pool_stats_release() assumes that the
pointer to the svc_serv cannot become NULL while a reference is held.

This used to be the case but a recent patch split nfsd_last_thread() out
from nfsd_put(), and clearing the pointer is done in nfsd_last_thread().

This is easily reproduced by running
   rpc.nfsd 8 ; ( rpc.nfsd 0;true) < /proc/fs/nfsd/pool_stats

Fortunately nfsd_pool_stats_release() has easy access to the svc_serv
pointer, and so can call svc_put() on it directly.

Fixes: 9f28a971ee9f ("nfsd: separate nfsd_last_thread() from nfsd_put()")
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
1 parent fdd2630
Raw File
orphan.c 
// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2008 Red Hat.  All rights reserved.
 */

#include "ctree.h"
#include "disk-io.h"
#include "orphan.h"

int btrfs_insert_orphan_item(struct btrfs_trans_handle *trans,
			     struct btrfs_root *root, u64 offset)
{
	struct btrfs_path *path;
	struct btrfs_key key;
	int ret = 0;

	key.objectid = BTRFS_ORPHAN_OBJECTID;
	key.type = BTRFS_ORPHAN_ITEM_KEY;
	key.offset = offset;

	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;

	ret = btrfs_insert_empty_item(trans, root, path, &key, 0);

	btrfs_free_path(path);
	return ret;
}

int btrfs_del_orphan_item(struct btrfs_trans_handle *trans,
			  struct btrfs_root *root, u64 offset)
{
	struct btrfs_path *path;
	struct btrfs_key key;
	int ret = 0;

	key.objectid = BTRFS_ORPHAN_OBJECTID;
	key.type = BTRFS_ORPHAN_ITEM_KEY;
	key.offset = offset;

	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;

	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
	if (ret < 0)
		goto out;
	if (ret) { /* JDM: Really? */
		ret = -ENOENT;
		goto out;
	}

	ret = btrfs_del_item(trans, root, path);

out:
	btrfs_free_path(path);
	return ret;
}
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