From 9bd6c5913271eabcb7768a58197ed3301fe19f2d Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= Date: Sat, 4 Apr 2020 22:42:13 +0200 Subject: [PATCH] Fix use-afte-free in ip_reass() (CVE-2020-1983) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The q pointer is updated when the mbuf data is moved from m_dat to m_ext. m_ext buffer may also be realloc()'ed and moved during m_cat(): q should also be updated in this case. Reported-by: Aviv Sasson Signed-off-by: Marc-André Lureau Reviewed-by: Samuel Thibault --- src/ip_input.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/src/ip_input.c b/src/ip_input.c index aa514ae..89a01d4 100644 --- a/src/ip_input.c +++ b/src/ip_input.c @@ -327,8 +327,7 @@ insert: */ q = fp->frag_link.next; m = dtom(slirp, q); - - int was_ext = m->m_flags & M_EXT; + int delta = (char *)q - (m->m_flags & M_EXT ? m->m_ext : m->m_dat); q = (struct ipasfrag *)q->ipf_next; while (q != (struct ipasfrag *)&fp->frag_link) { @@ -351,8 +350,7 @@ insert: * then an m_ext buffer was alloced. But fp->ipq_next points to the old * buffer (in the mbuf), so we must point ip into the new buffer. */ - if (!was_ext && m->m_flags & M_EXT) { - int delta = (char *)q - m->m_dat; + if (m->m_flags & M_EXT) { q = (struct ipasfrag *)(m->m_ext + delta); } -- 2.26.0.106.g9fadedd637