On Tue, Dec 07, 2021 at 03:00:39PM +0100, Alexander A Sverdlin wrote:

From: Alexander Sverdlin alexander.sverdlin@nokia.com

Commit bd5ae9288d64 ("nfsd: register pernet ops last, unregister first") has re-opened rpc_pipefs_event() race against nfsd_net_id registration (register_pernet_subsys()) which has been fixed by commit bb7ffbf29e76 ("nfsd: fix nsfd startup race triggering BUG_ON").

Restore the order of register_pernet_subsys() vs register_cld_notifier(). Add WARN_ON() to prevent a future regression.

That makes sense, thanks. I'll pass it along for 5.16.

--b.

Crash info: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000012 CPU: 8 PID: 345 Comm: mount Not tainted 5.4.144-... #1 pc : rpc_pipefs_event+0x54/0x120 [nfsd] lr : rpc_pipefs_event+0x48/0x120 [nfsd] Call trace: rpc_pipefs_event+0x54/0x120 [nfsd] blocking_notifier_call_chain rpc_fill_super get_tree_keyed rpc_fs_get_tree vfs_get_tree do_mount ksys_mount __arm64_sys_mount el0_svc_handler el0_svc

Fixes: bd5ae9288d64 ("nfsd: register pernet ops last, unregister first") Cc: stable@vger.kernel.org Signed-off-by: Alexander Sverdlin alexander.sverdlin@nokia.com

---

fs/nfsd/nfs4recover.c | 1 + fs/nfsd/nfsctl.c | 14 +++++++------- 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c index 6fedc49..4d829cf 100644 --- a/fs/nfsd/nfs4recover.c +++ b/fs/nfsd/nfs4recover.c @@ -2156,6 +2156,7 @@ static struct notifier_block nfsd4_cld_block = { int register_cld_notifier(void) {

• WARN_ON(!nfsd_net_id); return rpc_pipefs_notifier_register(&nfsd4_cld_block);

} diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c index af8531c..51a49e0 100644 --- a/fs/nfsd/nfsctl.c +++ b/fs/nfsd/nfsctl.c @@ -1521,12 +1521,9 @@ static int __init init_nfsd(void) int retval; printk(KERN_INFO "Installing knfsd (copyright (C) 1996 okir@monad.swb.de).\n");

• retval = register_cld_notifier();
• if (retval)

• return retval;
  

  retval = nfsd4_init_slabs(); if (retval)

• goto out_unregister_notifier;
  

• return retval;
  

  retval = nfsd4_init_pnfs(); if (retval) goto out_free_slabs;

@@ -1545,9 +1542,14 @@ static int __init init_nfsd(void) goto out_free_exports; retval = register_pernet_subsys(&nfsd_net_ops); if (retval < 0)

• goto out_free_filesystem;
  

• retval = register_cld_notifier();
• if (retval) goto out_free_all; return 0;

out_free_all:

• unregister_pernet_subsys(&nfsd_net_ops);

+out_free_filesystem: unregister_filesystem(&nfsd_fs_type); out_free_exports: remove_proc_entry("fs/nfs/exports", NULL); @@ -1561,13 +1563,12 @@ static int __init init_nfsd(void) nfsd4_exit_pnfs(); out_free_slabs: nfsd4_free_slabs(); -out_unregister_notifier:

• unregister_cld_notifier(); return retval;

} static void __exit exit_nfsd(void) {

• unregister_cld_notifier(); unregister_pernet_subsys(&nfsd_net_ops); nfsd_drc_slab_free(); remove_proc_entry("fs/nfs/exports", NULL);

@@ -1577,7 +1578,6 @@ static void __exit exit_nfsd(void) nfsd4_free_slabs(); nfsd4_exit_pnfs(); unregister_filesystem(&nfsd_fs_type);

• unregister_cld_notifier();

} MODULE_AUTHOR("Olaf Kirch okir@monad.swb.de"); -- 2.10.2