Patch "nfsd: fix nsfd startup race triggering BUG_ON" has been added to the 4.0-stable tree

This is a note to let you know that I've just added the patch titled

nfsd: fix nsfd startup race triggering BUG_ON

to the 4.0-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
nfsd-fix-nsfd-startup-race-triggering-bug_on.patch
and it can be found in the queue-4.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Giuseppe Cantavenera <[email protected]>
Date: Mon, 20 Apr 2015 18:00:08 +0200
Subject: nfsd: fix nsfd startup race triggering BUG_ON

From: Giuseppe Cantavenera <[email protected]>

commit bb7ffbf29e76b89a86ca4c3ee0d4690641f2f772 upstream.

nfsd triggered a BUG_ON in net_generic(...) when rpc_pipefs_event(...) in fs/nfsd/nfs4recover.c was called before assigning ntfsd_net_id. The following was observed on a MIPS 32-core processor:
kernel: Call Trace:
kernel: [<ffffffffc00bc5e4>] rpc_pipefs_event+0x7c/0x158 [nfsd]
kernel: [<ffffffff8017a2a0>] notifier_call_chain+0x70/0xb8
kernel: [<ffffffff8017a4e4>] __blocking_notifier_call_chain+0x4c/0x70
kernel: [<ffffffff8053aff8>] rpc_fill_super+0xf8/0x1a0
kernel: [<ffffffff8022204c>] mount_ns+0xb4/0xf0
kernel: [<ffffffff80222b48>] mount_fs+0x50/0x1f8
kernel: [<ffffffff8023dc00>] vfs_kern_mount+0x58/0xf0
kernel: [<ffffffff802404ac>] do_mount+0x27c/0xa28
kernel: [<ffffffff80240cf0>] SyS_mount+0x98/0xe8
kernel: [<ffffffff80135d24>] handle_sys64+0x44/0x68
kernel:
kernel:

        Code: 0040f809  00000000  2e020001 <00020336> 3c12c00d
                3c02801a  de100000 6442eb98  0040f809

kernel: ---[ end trace 7471374335809536 ]---

Fixed this behaviour by calling register_pernet_subsys(&nfsd_net_ops) before registering rpc_pipefs_event(...) with the notifier chain.

---
 fs/nfsd/nfsctl.c |   16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

@@ -1250,15 +1250,15 @@ static int __init init_nfsd(void)
 	int retval;
 	printk(KERN_INFO "Installing knfsd (copyright (C) 1996 [email protected]).\n");
 
-	retval = register_cld_notifier();
-	if (retval)
-		return retval;
 	retval = register_pernet_subsys(&nfsd_net_ops);
 	if (retval < 0)
-		goto out_unregister_notifier;
-	retval = nfsd4_init_slabs();
+		return retval;
+	retval = register_cld_notifier();
 	if (retval)
 		goto out_unregister_pernet;
+	retval = nfsd4_init_slabs();
+	if (retval)
+		goto out_unregister_notifier;
 	retval = nfsd4_init_pnfs();
 	if (retval)
 		goto out_free_slabs;

@@ -1290,10 +1290,10 @@ out_exit_pnfs:
 	nfsd4_exit_pnfs();
 out_free_slabs:
 	nfsd4_free_slabs();
-out_unregister_pernet:
-	unregister_pernet_subsys(&nfsd_net_ops);
 out_unregister_notifier:
 	unregister_cld_notifier();
+out_unregister_pernet:
+	unregister_pernet_subsys(&nfsd_net_ops);
 	return retval;
 }
 

@@ -1308,8 +1308,8 @@ static void __exit exit_nfsd(void)
 	nfsd4_exit_pnfs();
 	nfsd_fault_inject_cleanup();
 	unregister_filesystem(&nfsd_fs_type);
-	unregister_pernet_subsys(&nfsd_net_ops);
 	unregister_cld_notifier();
+	unregister_pernet_subsys(&nfsd_net_ops);
 }
 
 MODULE_AUTHOR("Olaf Kirch <[email protected]>");

Patches currently in stable-queue which might be from [email protected] are

queue-4.0/nfsd-fix-nsfd-startup-race-triggering-bug_on.patch