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>

diff --git a/net/nfs.c b/net/nfs.c
index 11941fad1acfc0381e26fd119eb311afef949b16..915acd95cf88dce0e613ecbdab18bbd41d25a547 100644 (file)
--- 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;