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From: Prasad J Pandit <pjp@fedoraproject.org>
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Date: Tue, 5 Jun 2018 23:38:35 +0530
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Subject: [PATCH] slirp: correct size computation while concatenating mbuf
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While reassembling incoming fragmented datagrams, 'm_cat' routine
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extends the 'mbuf' buffer, if it has insufficient room. It computes
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a wrong buffer size, which leads to overwriting adjacent heap buffer
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area. Correct this size computation in m_cat.
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Reported-by: ZDI Disclosures <zdi-disclosures@trendmicro.com>
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Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
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Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
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(cherry picked from commit 864036e251f54c99d31df124aad7f34f01f5344c)
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---
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slirp/mbuf.c | 11 +++++------
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slirp/mbuf.h | 8 +++-----
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2 files changed, 8 insertions(+), 11 deletions(-)
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diff --git a/slirp/mbuf.c b/slirp/mbuf.c
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index 5ff24559fd..18cbf759a7 100644
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--- a/slirp/mbuf.c
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+++ b/slirp/mbuf.c
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@@ -138,7 +138,7 @@ m_cat(struct mbuf *m, struct mbuf *n)
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* If there's no room, realloc
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*/
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if (M_FREEROOM(m) < n->m_len)
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- m_inc(m,m->m_size+MINCSIZE);
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+ m_inc(m, m->m_len + n->m_len);
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memcpy(m->m_data+m->m_len, n->m_data, n->m_len);
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m->m_len += n->m_len;
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@@ -147,7 +147,7 @@ m_cat(struct mbuf *m, struct mbuf *n)
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}
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-/* make m size bytes large */
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+/* make m 'size' bytes large from m_data */
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void
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m_inc(struct mbuf *m, int size)
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{
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@@ -158,12 +158,12 @@ m_inc(struct mbuf *m, int size)
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if (m->m_flags & M_EXT) {
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datasize = m->m_data - m->m_ext;
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- m->m_ext = g_realloc(m->m_ext, size);
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+ m->m_ext = g_realloc(m->m_ext, size + datasize);
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m->m_data = m->m_ext + datasize;
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} else {
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char *dat;
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datasize = m->m_data - m->m_dat;
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- dat = g_malloc(size);
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+ dat = g_malloc(size + datasize);
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memcpy(dat, m->m_dat, m->m_size);
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m->m_ext = dat;
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@@ -171,8 +171,7 @@ m_inc(struct mbuf *m, int size)
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m->m_flags |= M_EXT;
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}
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- m->m_size = size;
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-
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+ m->m_size = size + datasize;
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}
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diff --git a/slirp/mbuf.h b/slirp/mbuf.h
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index 893601ff9d..33b84485d6 100644
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--- a/slirp/mbuf.h
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+++ b/slirp/mbuf.h
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@@ -33,8 +33,6 @@
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#ifndef MBUF_H
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#define MBUF_H
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-#define MINCSIZE 4096 /* Amount to increase mbuf if too small */
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-
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/*
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* Macros for type conversion
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* mtod(m,t) - convert mbuf pointer to data pointer of correct type
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@@ -72,11 +70,11 @@ struct mbuf {
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struct mbuf *m_prevpkt; /* Flags aren't used in the output queue */
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int m_flags; /* Misc flags */
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- int m_size; /* Size of data */
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+ int m_size; /* Size of mbuf, from m_dat or m_ext */
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struct socket *m_so;
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- caddr_t m_data; /* Location of data */
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- int m_len; /* Amount of data in this mbuf */
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+ caddr_t m_data; /* Current location of data */
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+ int m_len; /* Amount of data in this mbuf, from m_data */
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Slirp *slirp;
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bool resolution_requested;
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