[PATCH 3.19.y-ckt 013/146] nfsd: fix nsfd startup race triggering BUG_ON

From: Kamal Mostafa
Date: Wed Jun 17 2015 - 19:43:58 EST

3.19.8-ckt2 -stable review patch. If anyone has any objections, please let me know.


From: Giuseppe Cantavenera <giuseppe.cantavenera.ext@xxxxxxxxx>

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
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.

Signed-off-by: Giuseppe Cantavenera <giuseppe.cantavenera.ext@xxxxxxxxx>
Signed-off-by: Lorenzo Restelli <lorenzo.restelli.ext@xxxxxxxxx>
Reviewed-by: Kinlong Mee <kinglongmee@xxxxxxxxx>
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
fs/nfsd/nfsctl.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 19ace74..336a06b 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -1249,15 +1249,15 @@ static int __init init_nfsd(void)
int retval;
printk(KERN_INFO "Installing knfsd (copyright (C) 1996 okir@xxxxxxxxxxxx).\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 = nfsd_fault_inject_init(); /* nfsd fault injection controls */
if (retval)
goto out_free_slabs;
@@ -1284,10 +1284,10 @@ out_free_stat:
- unregister_pernet_subsys(&nfsd_net_ops);
+ unregister_pernet_subsys(&nfsd_net_ops);
return retval;

@@ -1301,8 +1301,8 @@ static void __exit exit_nfsd(void)
- unregister_pernet_subsys(&nfsd_net_ops);
+ unregister_pernet_subsys(&nfsd_net_ops);

MODULE_AUTHOR("Olaf Kirch <okir@xxxxxxxxxxxx>");

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