linux-kernel - [PATCH] nfsd: Initialize ssc before laundromat

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Message-ID: <20250414143852.1308979-1-lilingfeng3@huawei.com>
Date: Mon, 14 Apr 2025 22:38:52 +0800
From: Li Lingfeng <lilingfeng3@...wei.com>
To: <chuck.lever@...cle.com>, <jlayton@...nel.org>, <neilb@...e.de>,
	<neil@...wn.name>, <okorniev@...hat.com>, <Dai.Ngo@...cle.com>,
	<tom@...pey.com>
CC: <linux-nfs@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<yukuai1@...weicloud.com>, <houtao1@...wei.com>, <yi.zhang@...wei.com>,
	<yangerkun@...wei.com>, <lilingfeng@...weicloud.com>,
	<lilingfeng3@...wei.com>
Subject: [PATCH] nfsd: Initialize ssc before laundromat_work to prevent NULL dereference

In nfs4_state_start_net(), laundromat_work may access nfsd_ssc through
nfs4_laundromat -> nfsd4_ssc_expire_umount. If nfsd_ssc isn't initialized,
this can cause NULL pointer dereference.

Normally the delayed start of laundromat_work allows sufficient time for
nfsd_ssc initialization to complete. However, when the kernel waits too
long for userspace responses (e.g. in nfs4_state_start_net ->
nfsd4_end_grace -> nfsd4_record_grace_done -> nfsd4_cld_grace_done ->
cld_pipe_upcall -> __cld_pipe_upcall -> wait_for_completion path), the
delayed work may start before nfsd_ssc initialization finishes.

Fix this by moving nfsd_ssc initialization before starting laundromat_work.

Fixes: f4e44b393389 ("NFSD: delay unmount source's export after inter-server copy completed.")
Signed-off-by: Li Lingfeng <lilingfeng3@...wei.com>
---
 fs/nfsd/nfssvc.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index 9b3d6cff0e1e..8ed143ef8b41 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -396,13 +396,13 @@ static int nfsd_startup_net(struct net *net, const struct cred *cred)
 	if (ret)
 		goto out_filecache;

+#ifdef CONFIG_NFSD_V4_2_INTER_SSC
+	nfsd4_ssc_init_umount_work(nn);
+#endif
 	ret = nfs4_state_start_net(net);
 	if (ret)
 		goto out_reply_cache;

-#ifdef CONFIG_NFSD_V4_2_INTER_SSC
-	nfsd4_ssc_init_umount_work(nn);
-#endif
 	nn->nfsd_net_up = true;
 	return 0;

-- 
2.31.1