X11rdp: check for errors from shmem calls

xorg/X11R7.6/rdp/rdpup.c

@@ -35,7 +35,7 @@ CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
     do { if (_level < LOG_LEVEL) { ErrorF _args ; ErrorF("\n"); } } while (0)
 
 static int g_use_shmem = 1; /* turns on or off */
-static int g_shmemid = 0;
+static int g_shmemid = -1;
 static char *g_shmemptr = 0;
 static int g_shmem_lineBytes = 0;
 static RegionPtr g_shm_reg = 0;
@@ -750,22 +750,36 @@ process_screen_size_msg(int width, int height, int bpp)
         if (g_shmemptr != 0)
         {
             shmdt(g_shmemptr);
+            g_shmemptr = 0;
         }
         bytes = g_rdpScreen.rdp_width * g_rdpScreen.rdp_height *
                 g_rdpScreen.rdp_Bpp;
         g_shmemid = shmget(IPC_PRIVATE, bytes, IPC_CREAT | 0777);
+        if (g_shmemid != -1)
+        {
             g_shmemptr = shmat(g_shmemid, 0, 0);
+            if (g_shmemptr == (void *) -1)
+            {
+                LLOGLN(0, ("process_screen_size_msg: shmat failed for %d "
+                       "bytes g_shmemid %d", bytes, g_shmemid));
+                g_shmemptr = 0;
                 shmctl(g_shmemid, IPC_RMID, NULL);
+                g_shmemid = -1;
+            }
+            else
+            {
+                shmctl(g_shmemid, IPC_RMID, NULL);
+            }
             LLOGLN(0, ("process_screen_size_msg: g_shmemid %d g_shmemptr %p",
                    g_shmemid, g_shmemptr));
             g_shmem_lineBytes = g_rdpScreen.rdp_Bpp * g_rdpScreen.rdp_width;
-
             if (g_shm_reg != 0)
             {
                 RegionDestroy(g_shm_reg);
             }
             g_shm_reg = RegionCreate(NullBox, 0);
         }
+    }
 
     mmwidth = PixelToMM(width);
     mmheight = PixelToMM(height);