[Qemu-devel] [PATCH v2] slirp: check data length while emulating ident function

[P J P <ppandit@redhat.com>]

From: Prasad J Pandit <pjp@fedoraproject.org>

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>
---
 slirp/tcp_subr.c | 4 ++++
 1 file changed, 4 insertions(+)

Update v2: return 1 instead of 0
  -> https://lists.gnu.org/archive/html/qemu-devel/2019-01/msg02182.html

diff --git a/slirp/tcp_subr.c b/slirp/tcp_subr.c
index fa61349cbb..8b1bd8c8c0 100644
--- a/slirp/tcp_subr.c
+++ b/slirp/tcp_subr.c
@@ -635,6 +635,10 @@ 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;
-- 
2.20.1