2015-11-16 19:57:41

by Jerry Snitselaar

Subject: [PATCH] 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.

Cc: "Steven Rostedt (Red Hat)" <[email protected]>
Signed-off-by: Jerry Snitselaar <[email protected]>
---
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);
--
2.6.1

2015-12-23 16:09:35

by Steven Rostedt

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

On Mon, 16 Nov 2015 12:57:28 -0700
Jerry Snitselaar <[email protected]> wrote:

> 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)" <[email protected]>
> Signed-off-by: Jerry Snitselaar <[email protected]>

I finally got around to applying this. Thanks!

-- Steve

> ---
> 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);