linux-kernel - Re: [RFC] globmatch() helper function

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Date:	Wed, 17 Dec 2008 11:13:12 -0500
From:	Steven Rostedt <srostedt@...hat.com>
To:	George Spelvin <linux@...izon.com>
Cc:	peterz@...radead.org, andi@...stfloor.org, tj@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC] globmatch() helper function


On Wed, 2008-12-17 at 11:04 -0500, George Spelvin wrote:

> 
> The problem is, what if some future thoughtless person feeds user data
> into the pattern argument?
> 
> I could just take support for non-trailing * out entirely.  That would be
> a different sort of documentation burden.
> 
> Or I could just add an explicit 2-level stack. If you overflow the stack,
> matching always fails.  Unfortunately, the code will be larger.
> 
> Do people think that would be, on balance, better?  It would be plenty
> good enough for the blacklist application.

Having a static function do the work and pass in a "depth" parameter
should be sufficient. As Andi mentioned, a depth of 10 should be plenty.

Like this:

static bool
 globmatch_internal(const char *pat, const char *str, int depth)
{
	if (depth > 10)
		return false;

	[...]

	while (!globmatch_internal(pat+1, str, depth+1))
	[...]
}

bool globmatch(const char *pat, const char *str)
{
	return globmatch_internal(pat, str, 0);
}

Make sure you include a "Signed-off-by:" as well.

-- Steve


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