Received-SPF: pass (google.com: domain of linux-nfs-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Zhang Xiaoxu <zhangxiaoxu5@huawei.com>
To:     <zhangxiaoxu5@huawei.com>, <bfields@fieldses.org>,
        <chuck.lever@oracle.com>, <linux-nfs@vger.kernel.org>,
        <yi.zhang@huawei.com>, <luomeng12@huawei.com>, <dai.ngo@oracle.com>
Subject: [v2 2/2] nfsd: Fix null-ptr-deref in nfsd_fill_super()
Date:   Sat, 21 May 2022 12:08:45 +0800
Message-ID: <20220521040845.619409-3-zhangxiaoxu5@huawei.com>
In-Reply-To: <20220521040845.619409-1-zhangxiaoxu5@huawei.com>
References: <20220521040845.619409-1-zhangxiaoxu5@huawei.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 7BIT
Content-Type:   text/plain; charset=US-ASCII
Precedence: bulk

KASAN report null-ptr-deref as follows:

  BUG: KASAN: null-ptr-deref in nfsd_fill_super+0xc6/0xe0 [nfsd]
  Write of size 8 at addr 000000000000005d by task a.out/852

  CPU: 7 PID: 852 Comm: a.out Not tainted 5.18.0-rc7-dirty #66
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc33 04/01/2014
  Call Trace:
   <TASK>
   dump_stack_lvl+0x34/0x44
   kasan_report+0xab/0x120
   ? nfsd_mkdir+0x71/0x1c0 [nfsd]
   ? nfsd_fill_super+0xc6/0xe0 [nfsd]
   nfsd_fill_super+0xc6/0xe0 [nfsd]
   ? nfsd_mkdir+0x1c0/0x1c0 [nfsd]
   get_tree_keyed+0x8e/0x100
   vfs_get_tree+0x41/0xf0
   __do_sys_fsconfig+0x590/0x670
   ? fscontext_read+0x180/0x180
   ? anon_inode_getfd+0x4f/0x70
   do_syscall_64+0x35/0x80
   entry_SYSCALL_64_after_hwframe+0x44/0xae

This can be reproduce by concurrent operations:
	1. fsopen(nfsd)/fsconfig
	2. insmod/rmmod nfsd

Since the nfsd file system is registered before than nfsd_net allocated,
the caller may get the file_system_type and use the nfsd_net before it
allocated, then null-ptr-deref occurred.

So init_nfsd() should call register_filesystem() last.

Fixes: bd5ae9288d64 ("nfsd: register pernet ops last, unregister first")
Cc: stable@kernel.org
Signed-off-by: Zhang Xiaoxu <zhangxiaoxu5@huawei.com>
---
 fs/nfsd/nfsctl.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 55949e60897d..0621c2faf242 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -1535,25 +1535,25 @@ static int __init init_nfsd(void)
 	retval = create_proc_exports_entry();
 	if (retval)
 		goto out_free_lockd;
-	retval = register_filesystem(&nfsd_fs_type);
-	if (retval)
-		goto out_free_exports;
 	retval = register_pernet_subsys(&nfsd_net_ops);
 	if (retval < 0)
-		goto out_free_filesystem;
+		goto out_free_exports;
 	retval = register_cld_notifier();
 	if (retval)
 		goto out_free_subsys;
 	retval = nfsd4_create_laundry_wq();
+	if (retval)
+		goto out_free_cld;
+	retval = register_filesystem(&nfsd_fs_type);
 	if (retval)
 		goto out_free_all;
 	return 0;
 out_free_all:
+	nfsd4_destroy_laundry_wq();
+out_free_cld:
 	unregister_cld_notifier();
 out_free_subsys:
 	unregister_pernet_subsys(&nfsd_net_ops);
-out_free_filesystem:
-	unregister_filesystem(&nfsd_fs_type);
 out_free_exports:
 	remove_proc_entry("fs/nfs/exports", NULL);
 	remove_proc_entry("fs/nfs", NULL);
@@ -1571,6 +1571,7 @@ static int __init init_nfsd(void)
 
 static void __exit exit_nfsd(void)
 {
+	unregister_filesystem(&nfsd_fs_type);
 	nfsd4_destroy_laundry_wq();
 	unregister_cld_notifier();
 	unregister_pernet_subsys(&nfsd_net_ops);
@@ -1581,7 +1582,6 @@ static void __exit exit_nfsd(void)
 	nfsd_lockd_shutdown();
 	nfsd4_free_slabs();
 	nfsd4_exit_pnfs();
-	unregister_filesystem(&nfsd_fs_type);
 }
 
 MODULE_AUTHOR("Olaf Kirch <okir@monad.swb.de>");
-- 
2.31.1