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

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Date:	Wed, 17 Dec 2008 16:15:42 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	George Spelvin <linux@...izon.com>, linux-kernel@...r.kernel.org,
	tj@...nel.org, Steven Rostedt <srostedt@...hat.com>
Subject: Re: [RFC] globmatch() helper function

On Wed, 2008-12-17 at 14:28 +0100, Andi Kleen wrote:
> "George Spelvin" <linux@...izon.com> writes:
> 
> Wow, finally a name.
> 
> > 			break;
> > 		case '*':
> > 			if (pat[1] == '\0')	/* Optimize trailing * case */
> > 				return true;
> > 			/* Recurse on each possible tail of str */
> > 			while (!globmatch(pat+1, str))
> > 				if (!*str++)
> > 					return false;
> 
> I'm uneasy with the unbounded recursion. Sure currently all the users
> are controlled in kernel source code and expect to put in sane patterns.
> But if someone ever adds a user controlled glob in some way it will be 
> trivial to crash/overwrite memory with the limited kernel stack.
> And with such a generalized function it's likely to be used more
> in the future.

ftrace has a globbing thing in there somewhere as well and that does
indeed take user input.

Using recursion in kernel code is indeed not recommended, what Andi said
we have tiny stacks.
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