Subject: Re: [RFC] globmatch() helper function
From: Peter Zijlstra <peterz@infradead.org>
To: Andi Kleen <andi@firstfloor.org>
Cc: George Spelvin <linux@horizon.com>, linux-kernel@vger.kernel.org,
        tj@kernel.org, Steven Rostedt <srostedt@redhat.com>
In-Reply-To: <87hc530w39.fsf@basil.nowhere.org>
References: <20081217104247.28440.qmail@science.horizon.com>
	 <87hc530w39.fsf@basil.nowhere.org>
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Date: Wed, 17 Dec 2008 16:15:42 +0100
Message-Id: <1229526942.9487.75.camel@twins>
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Sender: linux-kernel-owner@vger.kernel.org

On Wed, 2008-12-17 at 14:28 +0100, Andi Kleen wrote:
> "George Spelvin" <linux@horizon.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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