On Wed 2014-11-19 08:48:00, Steven Rostedt wrote:
> On Wed, 19 Nov 2014 12:40:17 +0100
> Petr Mladek <[email protected]> wrote:
>
> > > >
> > > > There is one more dangerous usage in trace_printk_seq(). It is on
> > > > three lines there.
> > >
> > > You totally confused me. What usage in trace_printk_seq(), and what
> > > three lines?
> > >
> > The confusion is caused by the 'k' ("print" vs. "printk") in the
> > function name. I was talking about the following function from
> > kernel/trace/trace.c:
>
> Silly 'k', Trix are for kids!
:-)
> >
> > void
> > trace_printk_seq(struct trace_seq *s)
> > {
> > /* Probably should print a warning here. */
> > if (s->seq.len >= TRACE_MAX_PRINT)
> > s->seq.len = TRACE_MAX_PRINT;
> >
> > /* should be zero ended, but we are paranoid. */
> > s->buffer[s->seq.len] = 0;
> >
> > printk(KERN_TRACE "%s", s->buffer);
> >
> > trace_seq_init(s);
> > }
> >
> > I found it when checking the applied patches in origin/rfc/seq-buf
> > branch. I hope that it was the correct place.
>
> Yes, that's the working branch for this code.
>
> Anyway, I saw this and thought about using trace_seq_used(), but then I
> realized that this is trace_seq code which has a hard coded buffer
> length of PAGE_SIZE which on all archs is more than 1000
> (TRACE_MAX_PRINT).
>
> Regardless of overflow or not (or even if trace_seq is full), that if
> statement will prevent this from doing any buffer overflows.
>
> s->seq.len will never be more than s->seq.size after the test against
> TRACE_MAX_PRINT. So I see no harm here.
Ah, I see. Well, I would feel more comfortable if it uses
trace_seq_used() or if there is some explanation in a comment.
But you are right, it is safe as it is. Feel free to leave it.
Reviewed-by: Petr Mladek <[email protected]>
Best Regards,
Petr
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
