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Commit c49c06e4 authored by Vivek Goyal's avatar Vivek Goyal Committed by Jens Axboe
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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: default avatarVivek Goyal <vgoyal@redhat.com>
Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
parent 9355aede

block/blk-throttle.c

+15 −1
Original line number Diff line number Diff line
@@ -430,6 +430,7 @@ static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg, 
	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 @@ static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg, 


	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)