Missing nullptr check in sys_openat

e4afcf9f · Silas Boyd-Wickizer · 93f8127a · e4afcf9f
--- a/kernel/sysfile.cc
+++ b/kernel/sysfile.cc
@@ -297,7 +297,7 @@ sys_openat(int dirfd, const char *path, int omode)
    return -1;
  } else {
    struct file *fdir = myproc()->ofile[dirfd];
-    if (fdir->type != file::FD_INODE)
+    if (fdir == nullptr || fdir->type != file::FD_INODE)
      return -1;
    cwd = fdir->ip;
  }