patch-2.4.22 linux-2.4.22/kernel/fork.c

• Lines: 46
• Date: 2003-08-25 04:44:44.000000000 -0700
• Orig file: linux-2.4.21/kernel/fork.c
• Orig date: 2003-06-13 07:51:39.000000000 -0700

diff -urN linux-2.4.21/kernel/fork.c linux-2.4.22/kernel/fork.c
@@ -448,6 +448,11 @@
 		goto out;
 	}
 
+	/*
+	 * Note: we may be using current for both targets (See exec.c)
+	 * This works because we cache current->files (old) as oldf. Don't
+	 * break this.
+	 */
 	tsk->files = NULL;
 	error = -ENOMEM;
 	newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL);
@@ -537,6 +542,33 @@
 	goto out;
 }
 
+/*
+ *	Helper to unshare the files of the current task. 
+ *	We don't want to expose copy_files internals to 
+ *	the exec layer of the kernel.
+ */
+
+int unshare_files(void)
+{
+	struct files_struct *files  = current->files;
+	int rc;
+	
+	if(!files)
+		BUG();
+		
+	/* This can race but the race causes us to copy when we don't
+	   need to and drop the copy */
+	if(atomic_read(&files->count) == 1)
+	{
+		atomic_inc(&files->count);
+		return 0;
+	}
+	rc = copy_files(0, current);
+	if(rc)
+		current->files = files;
+	return rc;
+}		
+
 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk)
 {
 	struct signal_struct *sig;