CVE-2019-14196: nfs: fix unbounded memcpy with a failed length check at nfs_lookup_reply

This patch adds a check to rpc_pkt.u.reply.data at nfs_lookup_reply.

Signed-off-by: Cheng Liu <liucheng32@huawei.com>
Reported-by: Fermín Serna <fermin@semmle.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>

diff --git a/net/nfs.c b/net/nfs.c
index 915acd9..89952ae 100644 (file)
--- a/net/nfs.c
+++ b/net/nfs.c
@@ -566,11 +566,15 @@ static int nfs_lookup_reply(uchar *pkt, unsigned len)
        }
 
        if (supported_nfs_versions & NFSV2_FLAG) {
+               if (((uchar *)&(rpc_pkt.u.reply.data[0]) - (uchar *)(&rpc_pkt) + NFS_FHSIZE) > len)
+                       return -NFS_RPC_DROP;
                memcpy(filefh, rpc_pkt.u.reply.data + 1, NFS_FHSIZE);
        } else {  /* NFSV3_FLAG */
                filefh3_length = ntohl(rpc_pkt.u.reply.data[1]);
                if (filefh3_length > NFS3_FHSIZE)
                        filefh3_length  = NFS3_FHSIZE;
+               if (((uchar *)&(rpc_pkt.u.reply.data[0]) - (uchar *)(&rpc_pkt) + filefh3_length) > len)
+                       return -NFS_RPC_DROP;
                memcpy(filefh, rpc_pkt.u.reply.data + 2, filefh3_length);
        }