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Date: Thu, 03 Mar 2011 17:45:18 -0600
From: David Lambert <dave@lambsys.com>
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To: "linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>
Subject: Bug in mtd_speedtest?
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I think I may have found an overflow condition in the speed calculation 
of mtd_speedtest on some platforms with larger flash partitions:

Consider for example if goodebcnt = 15000, and mtd->erasesize = 
256*1024, then there is an intermediate product of  3932160000 which 
results in the sign bit being set on a 32 bit integer. Maybe k should be 
an unsigned long long?

.....
static long calc_speed(void)
{
     long ms, k, speed;

     ms = (finish.tv_sec - start.tv_sec) * 1000 +
          (finish.tv_usec - start.tv_usec) / 1000;
     k = goodebcnt * mtd->erasesize / 1024;
     speed = (k * 1000) / ms;
     return speed;
}
.....