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nfsd: Fix nsfd startup race (again)

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commit b10252c7ae upstream.

Commit bd5ae9288d ("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 bb7ffbf29e
("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.

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: bd5ae9288d ("nfsd: register pernet ops last, unregister first")
Cc: stable@vger.kernel.org
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Alexander Sverdlin 2021-12-07 15:00:39 +01:00 • committed by Greg Kroah-Hartman
commit c520943a00
2 changed files with 8 additions and 7 deletions
Download patch file Download diff file Expand all files Collapse all files

1
fs/nfsd/nfs4recover.c
View file

@ -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);
}

14
fs/nfsd/nfsctl.c
View file

@ -1525,12 +1525,9 @@ 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;
@ -1547,9 +1544,14 @@ 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);
@ -1562,13 +1564,12 @@ out_free_stat:
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);
@ -1578,7 +1579,6 @@ 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>");