[PATCH 1/4] tracing: disable seeking for trace_pipe_raw

[Lai Jiangshan <laijs@cn.fujitsu.com>]

Impact: disable pread()

We set tracing_buffers_fops.llseek to no_llseek,
but we can still perform pread() to read this file.
That is not expected.

This fix uses nonseekable_open() to disable it.

tracing_buffers_fops.llseek is still set to no_llseek,
it mark this file is a "non-seekable device" and is used by
sys_splice(). See also do_splice() or manual of splice(2):

ERRORS
       EINVAL Target file system doesn't support  splicing;
              neither  of the descriptors refers to a pipe;
              or offset given for non-seekable device.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 2a81dec..7283b99 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3265,7 +3265,7 @@ static int tracing_buffers_open(struct inode *inode, struct file *filp)
 
 	filp->private_data = info;
 
-	return 0;
+	return nonseekable_open(inode, filp);
 
  out:
 	kfree(info);