slirp: check data length while emulating ident function

While emulating identification protocol, tcp_emu() does not check
available space in the 'sc_rcv->sb_data' buffer. It could lead to
heap buffer overflow issue. Add check to avoid it.

Reported-by: Kira <864786842@qq.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

diff --git a/slirp/tcp_subr.c b/slirp/tcp_subr.c
index 4a9a5b5edc1dd9fec0400b23c8fa05eb4af90e0d..23a841f26e4453ca7c38babdaf029a556fb49110 100644 (file)
--- a/slirp/tcp_subr.c
+++ b/slirp/tcp_subr.c
@@ -634,6 +634,11 @@ tcp_emu(struct socket *so, struct mbuf *m)
                        socklen_t addrlen = sizeof(struct sockaddr_in);
                        struct sbuf *so_rcv = &so->so_rcv;
 
+                       if (m->m_len > so_rcv->sb_datalen
+                                       - (so_rcv->sb_wptr - so_rcv->sb_data)) {
+                           return 1;
+                       }
+
                        memcpy(so_rcv->sb_wptr, m->m_data, m->m_len);
                        so_rcv->sb_wptr += m->m_len;
                        so_rcv->sb_rptr += m->m_len;