[PATCH v3 1/3] pfinet: add MAP_FAILED check after mmap in S_pfinet_siocgifconf

The mmap call to allocate a buffer for SIOCGIFCONF had no
MAP_FAILED check before the buffer was passed to dev_ifconf.
If mmap fails under memory pressure, pfinet would crash
writing to address (void *)-1.

* pfinet/pfinet-ops.c (S_pfinet_siocgifconf): Check ifc.ifc_buf
for MAP_FAILED immediately after mmap, release global_lock and
return ENOMEM on failure.
---
 pfinet/pfinet-ops.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/pfinet/pfinet-ops.c b/pfinet/pfinet-ops.c
index fab57570..dd571bfb 100644
--- a/pfinet/pfinet-ops.c
+++ b/pfinet/pfinet-ops.c
@@ -77,8 +77,16 @@ S_pfinet_siocgifconf (io_t port,
     {
       /* Possibly allocate a new buffer. */
       if (*len < amount)
-	ifc.ifc_buf = (char *) mmap (0, amount, PROT_READ|PROT_WRITE,
-				     MAP_ANON, 0, 0);
+	{
+	  ifc.ifc_buf = (char *) mmap (0, amount, PROT_READ|PROT_WRITE,
+				       MAP_ANON, 0, 0);
+	  if (ifc.ifc_buf == MAP_FAILED)
+	    {
+        pthread_mutex_unlock(&global_lock);
+        /* Should use errno here, but glue headers #undef errno */    
+	      return ENOMEM;
+	    }
+	}
       else
 	ifc.ifc_buf = *ifr;
       err = dev_ifconf ((char *) &ifc);
-- 
2.54.0