[PATCH] nfsd: fix error handling of register_pernet_subsys() in init_nfsd()

[PATCH] nfsd: fix error handling of register_pernet_subsys() in init_nfsd()

[Ho, Patrick]

From 7417896fcc7aea645fa0b89f39fa55979251dca3 Mon Sep 17 00:00:00 2001
From: Patrick Ho <Patrick.Ho@netapp.com>
Date: Sat, 21 Aug 2021 02:56:26 -0400
Subject: [PATCH] nfsd: fix error handling of register_pernet_subsys() in
 init_nfsd()

init_nfsd() should not unregister pernet subsys if the register fails
but should instead unwind from the last successful operation which is
register_filesystem().

Unregistering a failed register_pernet_subsys() call can result in
a kernel GPF as revealed by programmatically injecting an error in
register_pernet_subsys().

Verified the fix handled failure gracefully with no lingering nfsd
entry in /proc/filesystems.  This change was introduced by the commit
bd5ae9288d64 ("nfsd: register pernet ops last, unregister first"),
the original error handling logic was correct.

Fixes: bd5ae9288d64 ("nfsd: register pernet ops last, unregister first")
Cc: stable@vger.kernel.org
Signed-off-by: Patrick Ho <Patrick.Ho@netapp.com>
---
 fs/nfsd/nfsctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index c2c3d9077dc5..09ae1a0873d0 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -1545,7 +1545,7 @@ static int __init init_nfsd(void)
 		goto out_free_all;
 	return 0;
 out_free_all:
-	unregister_pernet_subsys(&nfsd_net_ops);
+	unregister_filesystem(&nfsd_fs_type);
 out_free_exports:
 	remove_proc_entry("fs/nfs/exports", NULL);
 	remove_proc_entry("fs/nfs", NULL);
-- 
2.17.1

Re: [PATCH] nfsd: fix error handling of register_pernet_subsys() in init_nfsd()

[J. Bruce Fields]

On Thu, Sep 30, 2021 at 03:48:42AM +0000, Ho, Patrick wrote:
> >From 7417896fcc7aea645fa0b89f39fa55979251dca3 Mon Sep 17 00:00:00 2001
> From: Patrick Ho <Patrick.Ho@netapp.com>
> Date: Sat, 21 Aug 2021 02:56:26 -0400
> Subject: [PATCH] nfsd: fix error handling of register_pernet_subsys() in
>  init_nfsd()
> 
> init_nfsd() should not unregister pernet subsys if the register fails
> but should instead unwind from the last successful operation which is
> register_filesystem().
> 
> Unregistering a failed register_pernet_subsys() call can result in
> a kernel GPF as revealed by programmatically injecting an error in
> register_pernet_subsys().
> 
> Verified the fix handled failure gracefully with no lingering nfsd
> entry in /proc/filesystems.  This change was introduced by the commit
> bd5ae9288d64 ("nfsd: register pernet ops last, unregister first"),
> the original error handling logic was correct.

Whoops, thanks for catching this.  I assume Chuck will pick it up.

Acked-by: J. Bruce Fields <bfields@redhat.com>

--b.

> 
> Fixes: bd5ae9288d64 ("nfsd: register pernet ops last, unregister first")
> Cc: stable@vger.kernel.org
> Signed-off-by: Patrick Ho <Patrick.Ho@netapp.com>
> ---
>  fs/nfsd/nfsctl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
> index c2c3d9077dc5..09ae1a0873d0 100644
> --- a/fs/nfsd/nfsctl.c
> +++ b/fs/nfsd/nfsctl.c
> @@ -1545,7 +1545,7 @@ static int __init init_nfsd(void)
>  		goto out_free_all;
>  	return 0;
>  out_free_all:
> -	unregister_pernet_subsys(&nfsd_net_ops);
> +	unregister_filesystem(&nfsd_fs_type);
>  out_free_exports:
>  	remove_proc_entry("fs/nfs/exports", NULL);
>  	remove_proc_entry("fs/nfs", NULL);
> -- 
> 2.17.1

Re: [PATCH] nfsd: fix error handling of register_pernet_subsys() in init_nfsd()

[Chuck Lever III]

> On Sep 30, 2021, at 10:16 AM, J. Bruce Fields <bfields@fieldses.org> wrote:
> 
> On Thu, Sep 30, 2021 at 03:48:42AM +0000, Ho, Patrick wrote:
>>> From 7417896fcc7aea645fa0b89f39fa55979251dca3 Mon Sep 17 00:00:00 2001
>> From: Patrick Ho <Patrick.Ho@netapp.com>
>> Date: Sat, 21 Aug 2021 02:56:26 -0400
>> Subject: [PATCH] nfsd: fix error handling of register_pernet_subsys() in
>> init_nfsd()
>> 
>> init_nfsd() should not unregister pernet subsys if the register fails
>> but should instead unwind from the last successful operation which is
>> register_filesystem().
>> 
>> Unregistering a failed register_pernet_subsys() call can result in
>> a kernel GPF as revealed by programmatically injecting an error in
>> register_pernet_subsys().
>> 
>> Verified the fix handled failure gracefully with no lingering nfsd
>> entry in /proc/filesystems.  This change was introduced by the commit
>> bd5ae9288d64 ("nfsd: register pernet ops last, unregister first"),
>> the original error handling logic was correct.
> 
> Whoops, thanks for catching this.  I assume Chuck will pick it up.

Applied to the for-next branch at

git://git.kernel.org/pub/scm/linux/kernel/git/cel/linux.git



> Acked-by: J. Bruce Fields <bfields@redhat.com>
> 
> --b.
> 
>> 
>> Fixes: bd5ae9288d64 ("nfsd: register pernet ops last, unregister first")
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Patrick Ho <Patrick.Ho@netapp.com>
>> ---
>> fs/nfsd/nfsctl.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
>> index c2c3d9077dc5..09ae1a0873d0 100644
>> --- a/fs/nfsd/nfsctl.c
>> +++ b/fs/nfsd/nfsctl.c
>> @@ -1545,7 +1545,7 @@ static int __init init_nfsd(void)
>> 		goto out_free_all;
>> 	return 0;
>> out_free_all:
>> -	unregister_pernet_subsys(&nfsd_net_ops);
>> +	unregister_filesystem(&nfsd_fs_type);
>> out_free_exports:
>> 	remove_proc_entry("fs/nfs/exports", NULL);
>> 	remove_proc_entry("fs/nfs", NULL);
>> -- 
>> 2.17.1

--
Chuck Lever