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From: Peter Mamonov <pmamonov@gmail.com>
To: Sascha Hauer <s.hauer@pengutronix.de>
Cc: barebox@lists.infradead.org
Subject: Re: command: hashsum: md5sum reports wrong sum for the file named 4k.bin
Date: Fri, 5 Jan 2018 21:17:30 +0300	[thread overview]
Message-ID: <20180105181730.q65oevjnuixvn5k2@localhost> (raw)
In-Reply-To: <20180105114419.pfb3ouxfogen4y6f@pengutronix.de>

On Fri, Jan 05, 2018 at 12:44:19PM +0100, Sascha Hauer wrote:
> Hi Peter,
> 
> On Thu, Dec 21, 2017 at 01:48:11PM +0300, Peter Mamonov wrote:
> > 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()?
> 
> preventing parse_area_spec() from modifying start and size if it fails
> seems like a good idea.
> 
> However, this doesn't solve the problem, does it? parse_area_spec()
> only fails because the dot in 4k.bin is not valid, but if you name
> the file only '4k' then parse_area_spec() won't fail.
> The problem is that we cannot know whether '4k' is a file or an area.

You are right. However, there is no ambiguity in the "4k.bin" and similar 
cases, so we can fix at least this obvious problem.

Regards,
Peter

> 
> Right now I have no good idea how to make the command nonambiguous,
> but this will require an incompatible change to the commands arguments.
> 
> Sascha
> 
> 
> -- 
> Pengutronix e.K.                           |                             |
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  reply	other threads:[~2018-01-05 18:17 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-12-20 10:48 command: hashsum: md5sum reports wrong sum for the file named 4k.bin Peter Mamonov
2017-12-21 10:48 ` Peter Mamonov
2018-01-05 11:44   ` Sascha Hauer
2018-01-05 18:17     ` Peter Mamonov [this message]
2018-01-09 11:10       ` Sascha Hauer
2018-01-09 14:21         ` [PATCH] lib: parse_area_spec: don't modify *start and *size values if parse failed Peter Mamonov
2018-01-11  8:15           ` Sascha Hauer
2018-01-11 17:28             ` Peter Mamonov
2018-01-15 11:32             ` [PATCH v2 1/3] lib: parse_area_spec: don't modify *start value " Peter Mamonov
2018-01-15 11:32               ` [PATCH v2 2/3] lib: parse_area_spec: part of the area spec after -/+ should start with a digit Peter Mamonov
2018-01-15 11:32               ` [PATCH v2 3/3] lib: parse_area_spec: no extra symbols after area spec are allowed except for spaces Peter Mamonov
2018-01-17  8:11               ` [PATCH v2 1/3] lib: parse_area_spec: don't modify *start value if parse failed Sascha Hauer
2018-01-17  9:31                 ` Peter Mamonov

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