nfsd4: fix crash on writing v4_end_grace before nfsd startup

Anatoly Trosinenko reports that this: 1) Checkout fresh master Linux branch (tested with commit e195ca6) 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 <[email protected]> Signed-off-by: J. Bruce Fields <[email protected]>
josf · Nov 28, 2018 · 62a063b · 62a063b
1 parent b8db159
commit 62a063b
Showing 1 changed file with 2 additions and 0 deletions.
diff --git 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: