Messages in this thread Patch in this message | | | From | Kamal Mostafa <> | Subject | [PATCH 030/104] cfq: explicitly use 64bit divide operation for 64bit arguments | Date | Thu, 10 Oct 2013 08:41:18 -0700 |
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3.8.13.11 -stable review patch. If anyone has any objections, please let me know.
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From: Anatol Pomozov <anatol.pomozov@gmail.com>
commit f3cff25f05f2ac29b2ee355e611b0657482f6f1d upstream.
'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> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- block/cfq-iosched.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index e62e920..1a872282 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -1484,7 +1484,7 @@ 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; -- 1.8.1.2
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