[PATCH] tracing: use seq_buf_used() in seq_buf_to_user() instead of len

From: Jerry Snitselaar
Date: Mon Nov 16 2015 - 14:57:44 EST

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.

Cc: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>
Signed-off-by: Jerry Snitselaar <jsnitsel@xxxxxxxxxx>
lib/seq_buf.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/lib/seq_buf.c b/lib/seq_buf.c
index 5c94e10..cb18469 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);

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