blkio-throttle: Fix possible multiplication overflow in iops calculations (c49c06e4) · Commits · 戴 / test

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>

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)

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