linux-kernel - Re: [PATCH] Smackv10: Smack rules grammar + their stateful parser

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Date:	Sun, 4 Nov 2007 00:12:58 +0200
From:	"Ahmed S. Darwish" <darwish.07@...il.com>
To:	"Kyle Moffett" <mrmacman_g4@....com>
Cc:	"Casey Schaufler" <casey@...aufler-ca.com>, akpm@...l.org,
	torvalds@...l.org, linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Smackv10: Smack rules grammar + their stateful parser

On 11/3/07, Kyle Moffett <mrmacman_g4@....com> wrote:
> On Nov 03, 2007, at 12:43:06, Ahmed S. Darwish wrote:
> > Bashv3 builtin "echo" behaves very strangely to -EINVAL. It sends
> > all the buffers that causes -EINVAL again in subsequent echo
> > invocations.
> >
> > i.e.
> > echo "Invalid Rule" > /smack/load  # -EINVAL returned
> > echo "Valid Rule" > /smack/load
> >
> > In seconod iteration, echo sends the first invalid buffer again
> > then sends the new one. This causes a "Invalid Rule\nValid Rule"
> > buffer sent to write().
> >
> > IMHO, this is a bug in builtin echo. The external /bin/echo doesn't
> > cause such strange behaviour.
>
> Actually, what causes problems here is something between a bug and a
> feature in libc's buffering.  Basically the -EINVAL error causes libc
> to leave its data in the file-output buffer despite the file being
> closed and reopened. Since a standalone echo just exits that buffer
> is discarded, but for the bash builtin it hangs around in the buffer
> for a while and ends up getting prepended to the following echo
> statement.  There's actually multiple ways to make this fail; this is
> just the simplest.
>

Thanks a lot for such a useful info. Is there a way from my side  to
make subsequent echo invocations not affected by previous failed ones
?

Regards,

-- 
Ahmed S. Darwish
Homepage: http://darwish.07.googlepages.com
Blog: http://darwish-07.blogspot.com
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