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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: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Vivek Goyal 2010-10-01 21:16:42 +02:00 committed by Jens Axboe
parent 9355aede5a
commit c49c06e496
1 changed files with 15 additions and 1 deletions
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16
block/blk-throttle.c
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@ -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)