The mbuf code currently doesn't check the result of doing a malloc()
or realloc() of its data (spotted by Coverity, CID 1238946).
Since the m_inc() API assumes that extending an mbuf must succeed,
just convert to g_malloc() and g_free().

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 slirp/mbuf.c | 30 ++++++++++++++----------------
 1 file changed, 14 insertions(+), 16 deletions(-)

diff --git a/slirp/mbuf.c b/slirp/mbuf.c
index 7eddc21..5ff2455 100644
--- a/slirp/mbuf.c
+++ b/slirp/mbuf.c
@@ -10,7 +10,7 @@
  * FreeBSD.  They are fixed size, determined by the MTU,
  * so that one whole packet can fit.  Mbuf's cannot be
  * chained together.  If there's more data than the mbuf
- * could hold, an external malloced buffer is pointed to
+ * could hold, an external g_malloced buffer is pointed to
  * by m_ext (and the data pointers) and M_EXT is set in
  * the flags
  */
@@ -41,26 +41,26 @@ void m_cleanup(Slirp *slirp)
     while ((struct quehead *) m != &slirp->m_usedlist) {
         next = m->m_next;
         if (m->m_flags & M_EXT) {
-            free(m->m_ext);
+            g_free(m->m_ext);
         }
-        free(m);
+        g_free(m);
         m = next;
     }
     m = (struct mbuf *) slirp->m_freelist.qh_link;
     while ((struct quehead *) m != &slirp->m_freelist) {
         next = m->m_next;
-        free(m);
+        g_free(m);
         m = next;
     }
 }
 
 /*
  * Get an mbuf from the free list, if there are none
- * malloc one
+ * allocate one
  *
  * Because fragmentation can occur if we alloc new mbufs and
  * free old mbufs, we mark all mbufs above mbuf_thresh as M_DOFREE,
- * which tells m_free to actually free() it
+ * which tells m_free to actually g_free() it
  */
 struct mbuf *
 m_get(Slirp *slirp)
@@ -71,8 +71,7 @@ m_get(Slirp *slirp)
 	DEBUG_CALL("m_get");
 
 	if (slirp->m_freelist.qh_link == &slirp->m_freelist) {
-		m = (struct mbuf *)malloc(SLIRP_MSIZE);
-		if (m == NULL) goto end_error;
+                m = g_malloc(SLIRP_MSIZE);
 		slirp->mbuf_alloced++;
 		if (slirp->mbuf_alloced > MBUF_THRESH)
 			flags = M_DOFREE;
@@ -94,7 +93,6 @@ m_get(Slirp *slirp)
         m->m_prevpkt = NULL;
         m->resolution_requested = false;
         m->expiration_date = (uint64_t)-1;
-end_error:
 	DEBUG_ARG("m = %p", m);
 	return m;
 }
@@ -112,15 +110,15 @@ m_free(struct mbuf *m)
 	   remque(m);
 
 	/* If it's M_EXT, free() it */
-	if (m->m_flags & M_EXT)
-	   free(m->m_ext);
-
+        if (m->m_flags & M_EXT) {
+                g_free(m->m_ext);
+        }
 	/*
 	 * Either free() it or put it on the free list
 	 */
 	if (m->m_flags & M_DOFREE) {
 		m->slirp->mbuf_alloced--;
-		free(m);
+                g_free(m);
 	} else if ((m->m_flags & M_FREELIST) == 0) {
 		insque(m,&m->slirp->m_freelist);
 		m->m_flags = M_FREELIST; /* Clobber other flags */
@@ -130,7 +128,7 @@ m_free(struct mbuf *m)
 
 /*
  * Copy data from one mbuf to the end of
- * the other.. if result is too big for one mbuf, malloc()
+ * the other.. if result is too big for one mbuf, allocate
  * an M_EXT data segment
  */
 void
@@ -160,12 +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 = (char *)realloc(m->m_ext,size);
+          m->m_ext = g_realloc(m->m_ext, size);
 	  m->m_data = m->m_ext + datasize;
         } else {
 	  char *dat;
 	  datasize = m->m_data - m->m_dat;
-	  dat = (char *)malloc(size);
+          dat = g_malloc(size);
 	  memcpy(dat, m->m_dat, m->m_size);
 
 	  m->m_ext = dat;
-- 
2.1.4

On 02/04/2017 08:08 PM, Peter Maydell wrote:
> The mbuf code currently doesn't check the result of doing a malloc()
> or realloc() of its data (spotted by Coverity, CID 1238946).
> Since the m_inc() API assumes that extending an mbuf must succeed,
> just convert to g_malloc() and g_free().
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

> ---
>  slirp/mbuf.c | 30 ++++++++++++++----------------
>  1 file changed, 14 insertions(+), 16 deletions(-)
>
> diff --git a/slirp/mbuf.c b/slirp/mbuf.c
> index 7eddc21..5ff2455 100644
> --- a/slirp/mbuf.c
> +++ b/slirp/mbuf.c
> @@ -10,7 +10,7 @@
>   * FreeBSD.  They are fixed size, determined by the MTU,
>   * so that one whole packet can fit.  Mbuf's cannot be
>   * chained together.  If there's more data than the mbuf
> - * could hold, an external malloced buffer is pointed to
> + * could hold, an external g_malloced buffer is pointed to
>   * by m_ext (and the data pointers) and M_EXT is set in
>   * the flags
>   */
> @@ -41,26 +41,26 @@ void m_cleanup(Slirp *slirp)
>      while ((struct quehead *) m != &slirp->m_usedlist) {
>          next = m->m_next;
>          if (m->m_flags & M_EXT) {
> -            free(m->m_ext);
> +            g_free(m->m_ext);
>          }
> -        free(m);
> +        g_free(m);
>          m = next;
>      }
>      m = (struct mbuf *) slirp->m_freelist.qh_link;
>      while ((struct quehead *) m != &slirp->m_freelist) {
>          next = m->m_next;
> -        free(m);
> +        g_free(m);
>          m = next;
>      }
>  }
>
>  /*
>   * Get an mbuf from the free list, if there are none
> - * malloc one
> + * allocate one
>   *
>   * Because fragmentation can occur if we alloc new mbufs and
>   * free old mbufs, we mark all mbufs above mbuf_thresh as M_DOFREE,
> - * which tells m_free to actually free() it
> + * which tells m_free to actually g_free() it
>   */
>  struct mbuf *
>  m_get(Slirp *slirp)
> @@ -71,8 +71,7 @@ m_get(Slirp *slirp)
>  	DEBUG_CALL("m_get");
>
>  	if (slirp->m_freelist.qh_link == &slirp->m_freelist) {
> -		m = (struct mbuf *)malloc(SLIRP_MSIZE);
> -		if (m == NULL) goto end_error;
> +                m = g_malloc(SLIRP_MSIZE);
>  		slirp->mbuf_alloced++;
>  		if (slirp->mbuf_alloced > MBUF_THRESH)
>  			flags = M_DOFREE;
> @@ -94,7 +93,6 @@ m_get(Slirp *slirp)
>          m->m_prevpkt = NULL;
>          m->resolution_requested = false;
>          m->expiration_date = (uint64_t)-1;
> -end_error:
>  	DEBUG_ARG("m = %p", m);
>  	return m;
>  }
> @@ -112,15 +110,15 @@ m_free(struct mbuf *m)
>  	   remque(m);
>
>  	/* If it's M_EXT, free() it */
> -	if (m->m_flags & M_EXT)
> -	   free(m->m_ext);
> -
> +        if (m->m_flags & M_EXT) {
> +                g_free(m->m_ext);
> +        }
>  	/*
>  	 * Either free() it or put it on the free list
>  	 */
>  	if (m->m_flags & M_DOFREE) {
>  		m->slirp->mbuf_alloced--;
> -		free(m);
> +                g_free(m);
>  	} else if ((m->m_flags & M_FREELIST) == 0) {
>  		insque(m,&m->slirp->m_freelist);
>  		m->m_flags = M_FREELIST; /* Clobber other flags */
> @@ -130,7 +128,7 @@ m_free(struct mbuf *m)
>
>  /*
>   * Copy data from one mbuf to the end of
> - * the other.. if result is too big for one mbuf, malloc()
> + * the other.. if result is too big for one mbuf, allocate
>   * an M_EXT data segment
>   */
>  void
> @@ -160,12 +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 = (char *)realloc(m->m_ext,size);
> +          m->m_ext = g_realloc(m->m_ext, size);
>  	  m->m_data = m->m_ext + datasize;
>          } else {
>  	  char *dat;
>  	  datasize = m->m_data - m->m_dat;
> -	  dat = (char *)malloc(size);
> +          dat = g_malloc(size);
>  	  memcpy(dat, m->m_dat, m->m_size);
>
>  	  m->m_ext = dat;
>