________________________________
From: Hashim Aziz <hasha...@hotmail.com>
Sent: 19 June 2020 7:19 PM
To: cygwin <cygwin@cygwin.com>
Subject: DD bug fails to wipe last 48 sectors of a disk


I first came across this bug last year, and wrote up my findings in a detailed 
answer to the StackExchange network:



https://superuser.com/questions/1505715/why-does-dd-give-me-an-error-at-the-end-of-zero-writing-a-disk



I didn’t then have the time to report it to this mailing list, but have just 
tested it using the latest version of Cygwin on the same two disks as I did 
then, and can confirm that the problem still persists. It’s also of note that I 
was running Windows 7 back then and am currently running 10, so this is now 
confirmed to manifest on both of the last two Windows OSes. I’m happy to work 
with the team to get this fixed, as I frequently need to make use of Cygwin dd 
to zero out drives for both security and regulatory compliance reasons, and 
failing to wipe the last 48 sectors of all drives is a pretty significant 
security risk.



Thanks,

Hashim



---


Apologies for the late reply, I've just finished going through the responses. 
While the code solutions given are useful and very interesting, they seem to be 
largely hacks and workarounds. As someone who wipes many drives for security 
purposes, from a security point of view it's a huge problem for dd to be 
silently and consistently failing to wipe the last sector of a drive, and 64KB 
is still plenty of space to contain sensitive documents. Is it planned for this 
to be fixed at some point?
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