Commit f3cff25f authored Sep 22, 2013 by Anatol Pomozov Committed by Jens Axboe Sep 22, 2013

cfq: explicitly use 64bit divide operation for 64bit arguments



'samples' is 64bit operant, but do_div() second parameter is 32.
do_div silently truncates high 32 bits and calculated result
is invalid.

In case if low 32bit of 'samples' are zeros then do_div() produces
kernel crash.

Signed-off-by: Anatol Pomozov <anatol.pomozov@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 75afb352

block/cfq-iosched.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1803,7 +1803,7 @@ static u64 cfqg_prfill_avg_queue_size(struct seq_file *sf,

		if (samples) {
		v = blkg_stat_read(&cfqg->stats.avg_queue_size_sum);
		do_div(v, samples);
		v = div64_u64(v, samples);
		}
		__blkg_prfill_u64(sf, pd, v);
		return 0;