[Patch] statistics: fix buffer overflow in histogram with linear scale

[Patch] statistics: fix buffer overflow in histogram with linear scale

[Martin Peschke]

Values outside the range covered by a histogram with linear
scale resulted in invalid indices pointing to non-existing
'buckets'. Index is adjusted to array boundaries, if required.

Signed-off-by: Martin Peschke <mp3@de.ibm.com>
---

 statistic.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diff -urp a/lib/statistic.c b/lib/statistic.c
--- a/lib/statistic.c	2006-10-08 23:03:56.000000000 +0200
+++ b/lib/statistic.c	2006-10-12 19:38:08.000000000 +0200
@@ -994,9 +994,12 @@ static s64 statistic_histogram_calc_valu
 
 static int statistic_histogram_calc_index_lin(struct statistic *stat, s64 value)
 {
-	unsigned long long i = value - stat->u.histogram.range_min;
+	unsigned long long i;
+	if (value <= stat->u.histogram.range_min)
+		return 0;
+	i = value - stat->u.histogram.range_min;
 	do_div(i, stat->u.histogram.base_interval);
-	return i;
+	return min(i, (unsigned long long)(stat->u.histogram.last_index));
 }
 
 static int statistic_histogram_calc_index_log2(struct statistic *stat,

Re: [Patch] statistics: fix buffer overflow in histogram with linear scale

[Andrew Morton]

On Fri, 20 Oct 2006 15:58:44 +0200
Martin Peschke <mp3@de.ibm.com> wrote:

> --- a/lib/statistic.c	2006-10-08 23:03:56.000000000 +0200
> +++ b/lib/statistic.c	2006-10-12 19:38:08.000000000 +0200

So...  what are we going to do with the statistics stuff?  It needs users
to prove its desirability/suitability.  I think there was some work done in
the SCSI area - did that come to anything?

Re: [Patch] statistics: fix buffer overflow in histogram with linear scale

[Frank Ch. Eigler]

Andrew Morton <akpm@osdl.org> writes:

> So...  what are we going to do with the statistics stuff?  It needs users
> to prove its desirability/suitability.  I think there was some work done in
> the SCSI area - did that come to anything?

There may be an opportunity here for combining this and the
markers-based lttng work.  Statistics gathering would be just one of
several possible back-end for events corresponding to scsi quantity
changes: tracing or more elaborate probing would also be enabled.

- FChE