NFSv4.1: allow zero fh array in filelayout decode layout

Signed-off-by: Andy Adamson <andros@netapp.com>
cc:stable@kernel.org [2.6.39]
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4filelayout.c

@@ -552,13 +552,18 @@ filelayout_decode_layout(struct pnfs_layout_hdr *flo,
 		__func__, nfl_util, fl->num_fh, fl->first_stripe_index,
 		fl->pattern_offset);
 
-	if (!fl->num_fh)
+	/* Note that a zero value for num_fh is legal for STRIPE_SPARSE.
+	 * Futher checking is done in filelayout_check_layout */
+	if (fl->num_fh < 0 || fl->num_fh >
+	    max(NFS4_PNFS_MAX_STRIPE_CNT, NFS4_PNFS_MAX_MULTI_CNT))
 		goto out_err;
 
-	fl->fh_array = kzalloc(fl->num_fh * sizeof(struct nfs_fh *),
-			       gfp_flags);
-	if (!fl->fh_array)
-		goto out_err;
+	if (fl->num_fh > 0) {
+		fl->fh_array = kzalloc(fl->num_fh * sizeof(struct nfs_fh *),
+				       gfp_flags);
+		if (!fl->fh_array)
+			goto out_err;
+	}
 
 	for (i = 0; i < fl->num_fh; i++) {
 		/* Do we want to use a mempool here? */