CVE: CVE-2018-11806 Upstream-Status: Backport https://lists.gnu.org/archive/html/qemu-devel/2018-06/msg01012.html From dc21a9d2951f0a2a7e63633e2b5c68c54e4edc4b Mon Sep 17 00:00:00 2001 From: Jeremy Puhlman Date: Thu, 14 Jun 2018 01:28:49 +0000 Subject: [PATCH] CVE-2018-11806 QEMU: slirp: heap buffer overflow Subject: [Qemu-devel] [PATCH 1/2] slirp: correct size computation while concatenating mbuf Date: Tue, 5 Jun 2018 23:38:35 +0530 From: Prasad J Pandit While reassembling incoming fragmented datagrams, 'm_cat' routine extends the 'mbuf' buffer, if it has insufficient room. It computes a wrong buffer size, which leads to overwriting adjacent heap buffer area. Correct this size computation in m_cat. Reported-by: ZDI Disclosures Signed-off-by: Prasad J Pandit --- slirp/mbuf.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) Signed-off-by: Jeremy Puhlman --- slirp/mbuf.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/slirp/mbuf.c b/slirp/mbuf.c index 5ff2455..7fb4501 100644 --- a/slirp/mbuf.c +++ b/slirp/mbuf.c @@ -138,7 +138,7 @@ m_cat(struct mbuf *m, struct mbuf *n) * If there's no room, realloc */ if (M_FREEROOM(m) < n->m_len) - m_inc(m,m->m_size+MINCSIZE); + m_inc(m, m->m_len + n->m_len); memcpy(m->m_data+m->m_len, n->m_data, n->m_len); m->m_len += n->m_len; @@ -158,12 +158,12 @@ m_inc(struct mbuf *m, int size) if (m->m_flags & M_EXT) { datasize = m->m_data - m->m_ext; - m->m_ext = g_realloc(m->m_ext, size); + m->m_ext = g_realloc(m->m_ext, size + datasize); m->m_data = m->m_ext + datasize; } else { char *dat; datasize = m->m_data - m->m_dat; - dat = g_malloc(size); + dat = g_malloc(size + datasize); memcpy(dat, m->m_dat, m->m_size); m->m_ext = dat; @@ -171,7 +171,7 @@ m_inc(struct mbuf *m, int size) m->m_flags |= M_EXT; } - m->m_size = size; + m->m_size = size + datasize; } -- 2.13.3