command: hashsum: md5sum reports wrong sum for the file named 4k.bin

[Peter Mamonov]

On Wed, Dec 20, 2017 at 01:48:14PM +0300, Peter Mamonov wrote:
> Hi,
> 
> The md5sum command reports wrong sum for a file named 4k.bin and, I guess, for 
> other files named alike. Here are the commands to reproduce the bug:

The problem lays in __do_digest() function: 
 - it initializes variables `start` and `size` at commands/digest.c:38
 - then it calls parse_area_spec(*argv, &start, &size) at commands/digest.c:42
 - parse_area_spec() returns error as it should, however it changes the value 
 of the `start` at lib/misc.c:87.
 - this causes digest algo to skip leading 4k of the data from the file.

I'm not quite sure what is the best solution:
 - prevent parse_area_spec() from setting start if it fails?
 - reinitialize start/size after unsuccessfull call to parse_area_spec()?

Regards,
Peter


> 
> 	barebox at barebox sandbox:/ memcpy -s /dev/zero -d _4k.bin 0 0 4k
> 	barebox at barebox sandbox:/ md5sum _4k.bin
> 	620f0b67a91f7f74151bc5be745b7110  _4k.bin
> 	
> 	barebox at barebox sandbox:/ cp _4k.bin 4k.bin
> 	barebox at barebox sandbox:/ md5sum 4k.bin
> 	d41d8cd98f00b204e9800998ecf8427e  4k.bin
> 	
> 	barebox at barebox sandbox:/ cp 4k.bin __4k.bin
> 	barebox at barebox sandbox:/ md5sum __4k.bin 
> 	620f0b67a91f7f74151bc5be745b7110  __4k.bin
> 	
> 	barebox at barebox sandbox:/ version
> 	
> 	barebox 2017.12.0 #4 Wed Dec 20 12:26:57 MSK 2017
> 	
> 	barebox at barebox sandbox:/ Terminated
> 	
> 	$ dd if=/dev/zero bs=4k count=1 | md5sum
> 	...
> 	620f0b67a91f7f74151bc5be745b7110  -
> 
> Regards,
> Peter