From: J. Bruce Fields <bfields@redhat.com>
Date: Tue, 27 Nov 2018 20:54:17 +0000 (-0500)
Subject: nfsd4: fix crash on writing v4_end_grace before nfsd startup
X-Git-Tag: v4.9.156~106
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=60846115bbedc018f66dbdee61f5880c96ca15ad;p=thirdparty%2Fkernel%2Fstable.git

nfsd4: fix crash on writing v4_end_grace before nfsd startup

[ 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>
---

diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c
index 36b2af931e06d..797a155c9a67a 100644
--- a/fs/nfsd/nfsctl.c
+++ b/fs/nfsd/nfsctl.c
@@ -1103,6 +1103,8 @@ 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: