From: Jia-Ju Bai <baijiaju1990@gmail.com>
Date: Fri, 26 Jul 2019 15:48:53 +0800
Subject: [PATCH] fs: nfs: Fix possible null-pointer dereferences in
 encode_attrs()
Git-commit: e2751463eaa6f9fec8fea80abbdc62dbc487b3c5
Patch-mainline: v5.4
References: git-fixes

In encode_attrs(), there is an if statement on line 1145 to check
whether label is NULL:
    if (label && (attrmask[2] & FATTR4_WORD2_SECURITY_LABEL))

When label is NULL, it is used on lines 1178-1181:
    *p++ = cpu_to_be32(label->lfs);
    *p++ = cpu_to_be32(label->pi);
    *p++ = cpu_to_be32(label->len);
    p = xdr_encode_opaque_fixed(p, label->label, label->len);

To fix these bugs, label is checked before being used.

These bugs are found by a static analysis tool STCheck written by us.

Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Acked-by: NeilBrown <neilb@suse.com>

---
 fs/nfs/nfs4xdr.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -1118,7 +1118,7 @@ static void encode_attrs(struct xdr_stre
 		} else
 			*p++ = cpu_to_be32(NFS4_SET_TO_SERVER_TIME);
 	}
-	if (bmval[2] & FATTR4_WORD2_SECURITY_LABEL) {
+	if (label && (bmval[2] & FATTR4_WORD2_SECURITY_LABEL)) {
 		*p++ = cpu_to_be32(label->lfs);
 		*p++ = cpu_to_be32(label->pi);
 		*p++ = cpu_to_be32(label->len);