tracing: Use seq_buf_used() in seq_buf_to_user() instead of len

commit 5ac48378414d ("tracing: Use trace_seq_used() and seq_buf_used()
instead of len") changed the tracing code to use trace_seq_used() and
seq_buf_used() instead of using the seq_buf len directly to avoid
overflow issues, but missed a spot in seq_buf_to_user() that makes use
of s->len.

Cleaned up the code a bit as well per suggestion of Steve Rostedt.

Link: http://lkml.kernel.org/r/1447703848-2951-1-git-send-email-jsnitsel@redhat.com

Signed-off-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/lib/seq_buf.c b/lib/seq_buf.c
index 5c94e1012a91..cb18469e1f49 100644
--- a/lib/seq_buf.c
+++ b/lib/seq_buf.c
@@ -306,10 +306,12 @@ int seq_buf_to_user(struct seq_buf *s, char __user *ubuf, int cnt)
         if (!cnt)
                 return 0;
 
-        if (s->len <= s->readpos)
+        len = seq_buf_used(s);
+
+        if (len <= s->readpos)
                 return -EBUSY;
 
-        len = seq_buf_used(s) - s->readpos;
+        len -= s->readpos;
         if (cnt > len)
                 cnt = len;
         ret = copy_to_user(ubuf, s->buffer + s->readpos, cnt);