On Wed, 19 Nov 2014 15:40:05 +0100 Petr Mladek <pmla...@suse.cz> wrote:
> > 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. > OK, I added this just for you: BTW, using trace_seq_used() would not be good enough because it could return s->seq.size. Which would overflow the buffer on the s->buffer[s->seq.len] = 0; -- Steve >From 1922acc9987d23d0b9c1ad28dc3eaafc1cf2d6b7 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" <rost...@goodmis.org> Date: Wed, 19 Nov 2014 10:56:41 -0500 Subject: [PATCH] tracing: Add paranoid size check in trace_printk_seq() To be really paranoid about writing out of bound data in trace_printk_seq(), add another check of len compared to size. Link: http://lkml.kernel.org/r/20141119144004.gb2...@dhcp128.suse.cz Suggested-by: Petr Mladek <pmla...@suse.cz> Signed-off-by: Steven Rostedt <rost...@goodmis.org> --- kernel/trace/trace.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 9023446b2c2b..26facec4625e 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -6656,6 +6656,14 @@ trace_printk_seq(struct trace_seq *s) if (s->seq.len >= TRACE_MAX_PRINT) s->seq.len = TRACE_MAX_PRINT; + /* + * More paranoid code. Although the buffer size is set to + * PAGE_SIZE, and TRACE_MAX_PRINT is 1000, this is just + * an extra layer of protection. + */ + if (WARN_ON_ONCE(s->seq.len >= s->seq.size)) + s->seq.len = s->seq.size - 1; + /* should be zero ended, but we are paranoid. */ s->buffer[s->seq.len] = 0; -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/