Commit-Id: ce131029d6d4a405cb7d3ac6716d03e58fb4a5d9 From: Prasad J Pandit Date: Thu, 9 Jan 2020 15:12:27 +0530 Subject: slirp: use correct size while emulating IRC commands Bug-Debian: http://bugs.debian.org/949084 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: Vishnu Dev TJ Signed-off-by: Prasad J Pandit Reviewed-by: Samuel Thibault Message-Id: <20200109094228.79764-2-ppandit@redhat.com> --- slirp/tcp_subr.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/slirp/tcp_subr.c b/slirp/tcp_subr.c index fa61349cbb0..5429805f87b 100644 --- a/slirp/tcp_subr.c +++ b/slirp/tcp_subr.c @@ -778,7 +778,7 @@ 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, + 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); @@ -789,7 +789,7 @@ 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, + m->m_len += 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); @@ -800,7 +800,7 @@ 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, + m->m_len += 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);