linux-kernel - [PATCH 5.4 08/52] nfsd: fix error handling of register_pernet_subsys() in init

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Date:   Mon, 11 Oct 2021 15:45:37 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Patrick Ho <Patrick.Ho@...app.com>,
        "J. Bruce Fields" <bfields@...hat.com>,
        Chuck Lever <chuck.lever@...cle.com>
Subject: [PATCH 5.4 08/52] nfsd: fix error handling of register_pernet_subsys() in init_nfsd()

From: Patrick Ho <Patrick.Ho@...app.com>

commit 1d625050c7c2dd877e108e382b8aaf1ae3cfe1f4 upstream.

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@...r.kernel.org
Signed-off-by: Patrick Ho <Patrick.Ho@...app.com>
Acked-by: J. Bruce Fields <bfields@...hat.com>
Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/nfsd/nfsctl.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -1549,7 +1549,7 @@ 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);