Free pgdir in setupkvm in case of mappages failure

There is a potential memory leak when mappages() fails inside setupkvm(). A call to freevm() is added in this case so as to reclaim the lost mapping pages.

Free pgdir in setupkvm in case of mappages failure
03b30863 · Saarett · GitHub · 59cdd6c6 · 03b30863
--- a/vm.c
+++ b/vm.c
@@ -137,8 +137,10 @@ setupkvm(void)
    panic("PHYSTOP too high");
  for(k = kmap; k < &kmap[NELEM(kmap)]; k++)
    if(mappages(pgdir, k->virt, k->phys_end - k->phys_start,
-                (uint)k->phys_start, k->perm) < 0)
+                (uint)k->phys_start, k->perm) < 0) {
+      freevm(pgdir);
      return 0;
+    }
  return pgdir;
 }