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From:   Sasha Levin <sashal@kernel.org>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc:     "J. Bruce Fields" <bfields@redhat.com>,
        Sasha Levin <sashal@kernel.org>, linux-nfs@vger.kernel.org
Subject: [PATCH AUTOSEL 4.19 081/258] nfsd4: fix crash on writing v4_end_grace before nfsd startup
Date:   Mon, 28 Jan 2019 10:56:27 -0500
Message-Id: <20190128155924.51521-81-sashal@kernel.org>
In-Reply-To: <20190128155924.51521-1-sashal@kernel.org>
References: <20190128155924.51521-1-sashal@kernel.org>
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From: "J. Bruce Fields" <bfields@redhat.com>

[ Upstream commit 62a063b8e7d1db684db3f207261a466fa3194e72 ]

Anatoly Trosinenko reports that this:

1) Checkout fresh master Linux branch (tested with commit e195ca6cb)
2) Copy x84_64-config-4.14 to .config, then enable NFS server v4 and build
3) From `kvm-xfstests shell`:

results in NULL dereference in locks_end_grace.

Check that nfsd has been started before trying to end the grace period.

Reported-by: Anatoly Trosinenko <anatoly.trosinenko@gmail.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/nfsd/nfsctl.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 7fb9f7c667b1..899174c7a8ae 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -1126,6 +1126,8 @@ static ssize_t write_v4_end_grace(struct file *file, char *buf, size_t size)
 		case 'Y':
 		case 'y':
 		case '1':
+			if (nn->nfsd_serv)
+				return -EBUSY;
 			nfsd4_end_grace(nn);
 			break;
 		default:
-- 
2.19.1