From 011880f527ff317a40769ea8673a6353e5db53ac Mon Sep 17 00:00:00 2001 From: Prasad J Pandit Date: Tue, 14 Apr 2020 18:23:23 +0800 Subject: [PATCH] slirp: use correct size while emulating IRC commands While emulating IRC DCC commands, tcp_emu() uses 'mbuf' size 'm->m_size' to write DCC commands via snprintf(3). This may lead to OOB write access, because 'bptr' points somewhere in the middle of 'mbuf' buffer, not at the start. Use M_FREEROOM(m) size to avoid OOB access. Reported-by: default avatarVishnu Dev TJ Signed-off-by: default avatarPrasad J Pandit Reviewed-by: Samuel Thibault's avatarSamuel Thibault Message-Id: <20200109094228.79764-2-ppandit@redhat.com> --- slirp/src/tcp_subr.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/slirp/src/tcp_subr.c b/slirp/src/tcp_subr.c index 9c94c03a..2a15b16a 100644 --- a/slirp/src/tcp_subr.c +++ b/slirp/src/tcp_subr.c @@ -778,7 +778,8 @@ int tcp_emu(struct socket *so, struct mbuf *m) return 1; } m->m_len = bptr - m->m_data; /* Adjust length */ - m->m_len += snprintf(bptr, m->m_size, "DCC CHAT chat %lu %u%c\n", + m->m_len += snprintf(bptr, M_FREEROOM(m), + "DCC CHAT chat %lu %u%c\n", (unsigned long)ntohl(so->so_faddr.s_addr), ntohs(so->so_fport), 1); } else if (sscanf(bptr, "DCC SEND %256s %u %u %u", buff, &laddr, &lport, @@ -789,7 +790,8 @@ int tcp_emu(struct socket *so, struct mbuf *m) } m->m_len = bptr - m->m_data; /* Adjust length */ m->m_len += - snprintf(bptr, m->m_size, "DCC SEND %s %lu %u %u%c\n", buff, + snprintf(bptr, M_FREEROOM(m), + "DCC SEND %s %lu %u %u%c\n", buff, (unsigned long)ntohl(so->so_faddr.s_addr), ntohs(so->so_fport), n1, 1); } else if (sscanf(bptr, "DCC MOVE %256s %u %u %u", buff, &laddr, &lport, @@ -800,7 +802,8 @@ int tcp_emu(struct socket *so, struct mbuf *m) } m->m_len = bptr - m->m_data; /* Adjust length */ m->m_len += - snprintf(bptr, m->m_size, "DCC MOVE %s %lu %u %u%c\n", buff, + snprintf(bptr, M_FREEROOM(m), + "DCC MOVE %s %lu %u %u%c\n", buff, (unsigned long)ntohl(so->so_faddr.s_addr), ntohs(so->so_fport), n1, 1); } -- 2.23.0