CVE-2019-14195: nfs: fix unbounded memcpy with unvalidated length at nfs_readlink_reply

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

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

1 files changed, 3 insertions, 0 deletions

diff --git a/net/nfs.c b/net/nfs.c
index 11941fad1a..915acd95cf 100644
--- a/net/nfs.c
+++ b/net/nfs.c
@@ -634,6 +634,9 @@ static int nfs_readlink_reply(uchar *pkt, unsigned len)
 	/* new path length */
 	rlen = ntohl(rpc_pkt.u.reply.data[1 + nfsv3_data_offset]);
 
+	if (((uchar *)&(rpc_pkt.u.reply.data[0]) - (uchar *)(&rpc_pkt) + rlen) > len)
+		return -NFS_RPC_DROP;
+
 	if (*((char *)&(rpc_pkt.u.reply.data[2 + nfsv3_data_offset])) != '/') {
 		int pathlen;