[Qemu-devel] [PATCH v1 0/2] correct size computation in m_cat

[Qemu-devel] [PATCH v1 0/2] correct size computation in m_cat

[P J P]

From: Prasad J Pandit <pjp@fedoraproject.org>

Hello,

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.

This patch set fixes this issue and formats m_cat() routine as per coding
style guide.

Update v1: fixed indentation
    https://lists.gnu.org/archive/html/qemu-devel/2018-06/msg01121.html

Thank you.
--
Prasad J Pandit (2):
  slirp: correct size computation while concatenating mbuf
  slirp: reformat m_cat routine

 slirp/mbuf.c | 41 +++++++++++++++++++----------------------
 1 file changed, 19 insertions(+), 22 deletions(-)

--
2.17.1

[Qemu-devel] [PATCH v1 1/2] slirp: correct size computation while concatenating mbuf

[P J P]

From: Prasad J Pandit <pjp@fedoraproject.org>

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 <zdi-disclosures@trendmicro.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
---
 slirp/mbuf.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

Update v1: fixed indentation
    https://lists.gnu.org/archive/html/qemu-devel/2018-06/msg01121.html

diff --git a/slirp/mbuf.c b/slirp/mbuf.c
index 5ff24559fd..6650981fc7 100644
--- a/slirp/mbuf.c
+++ b/slirp/mbuf.c
@@ -137,8 +137,9 @@ 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);
+    if (M_FREEROOM(m) < n->m_len) {
+        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 +159,12 @@ 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 +172,7 @@ m_inc(struct mbuf *m, int size)
 	  m->m_flags |= M_EXT;
         }
 
-        m->m_size = size;
+        m->m_size = size + datasize;
 
 }
 
-- 
2.17.1

[Qemu-devel] [PATCH v1 2/2] slirp: reformat m_cat routine

[P J P]

From: Prasad J Pandit <pjp@fedoraproject.org>

Coding style changes to the m_cat routine and minor refactoring.

Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
---
 slirp/mbuf.c | 36 ++++++++++++++++--------------------
 1 file changed, 16 insertions(+), 20 deletions(-)

diff --git a/slirp/mbuf.c b/slirp/mbuf.c
index 6650981fc7..e012cd4760 100644
--- a/slirp/mbuf.c
+++ b/slirp/mbuf.c
@@ -152,32 +152,28 @@ m_cat(struct mbuf *m, struct mbuf *n)
 void
 m_inc(struct mbuf *m, int size)
 {
-	int datasize;
+    int datasize;
 
-	/* some compiles throw up on gotos.  This one we can fake. */
-        if(m->m_size>size) return;
+    /* some compiles throw up on gotos. This one we can fake. */
+    if (m->m_size > size) {
+        return;
+    }
 
-        if (m->m_flags & M_EXT) {
-	  datasize = m->m_data - m->m_ext;
-          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 + datasize);
-	  memcpy(dat, m->m_dat, m->m_size);
-
-	  m->m_ext = dat;
-	  m->m_data = m->m_ext + datasize;
-	  m->m_flags |= M_EXT;
-        }
-
-        m->m_size = size + datasize;
+    if (m->m_flags & M_EXT) {
+        datasize = m->m_data - m->m_ext;
+        m->m_ext = g_realloc(m->m_ext, size + datasize);
+    } else {
+        datasize = m->m_data - m->m_dat;
+        m->m_ext = g_malloc(size + datasize);
+        memcpy(m->m_ext, m->m_dat, m->m_size);
+        m->m_flags |= M_EXT;
+    }
 
+    m->m_data = m->m_ext + datasize;
+    m->m_size = size + datasize;
 }
 
 
-
 void
 m_adj(struct mbuf *m, int len)
 {
-- 
2.17.1