blkio-throttle: Fix possible multiplication overflow in iops calculations
o User can specify max iops value of 32bit (UINT_MAX), through cgroup
interface. If a user has specified say 4294967294 (UNIT_MAX - 2), then
on 32bit platform, following multiplication can overflow.
io_allowed = (tg->iops[rw] * jiffy_elapsed_rnd)
o Explicitly cast the multiplication to 64bit and then perform division and
then check whether result is still great then UNINT_MAX.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index c1bc1b6..56ad453 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -430,6 +430,7 @@
bool rw = bio_data_dir(bio);
unsigned int io_allowed;
unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd;
+ u64 tmp;
jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw];
@@ -439,7 +440,20 @@
jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice);
- io_allowed = (tg->iops[rw] * jiffy_elapsed_rnd) / HZ;
+ /*
+ * jiffy_elapsed_rnd should not be a big value as minimum iops can be
+ * 1 then at max jiffy elapsed should be equivalent of 1 second as we
+ * will allow dispatch after 1 second and after that slice should
+ * have been trimmed.
+ */
+
+ tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd;
+ do_div(tmp, HZ);
+
+ if (tmp > UINT_MAX)
+ io_allowed = UINT_MAX;
+ else
+ io_allowed = tmp;
if (tg->io_disp[rw] + 1 <= io_allowed) {
if (wait)