linux-kernel - Re: [PATCH] lib: idr: fix out-of-bounds pointer dereference

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Date:	Tue, 24 Jun 2014 15:48:32 +0800
From:	Lai Jiangshan <laijs@...fujitsu.com>
To:	Andrey Ryabinin <a.ryabinin@...sung.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Tejun Heo <tj@...nel.org>, <linux-kernel@...r.kernel.org>,
	<tetra2005@...il.com>, <preobr@...gle.com>, <dvyukov@...gle.com>,
	<kcc@...gle.com>, <koct9i@...il.com>
Subject: Re: [PATCH] lib: idr: fix out-of-bounds pointer dereference


326cf0f0f308 ("idr: fix top layer handling") enlarged the pa array.
But the additional "+1" space is only used in id-allocation, it is free
in other usage, (paa may point to the additional "+1" space, but not dereference it).
so you can reuse it.

In the 3 functions your patch touched:
-	struct idr_layer ***paa = &pa[0];
+	struct idr_layer ***paa = &pa[1];


I don't reject your patch, I had review it.

Reviewed-by: Lai Jiangshan <laijs@...fujitsu.com>

The reason why I'm still muttering here is that I wish a simple solution
to fix the problem. And:
1) your patch also makes use of the additional "+1" @pa space: *++paa = p
2) your patch may slight enlarge the function body.
3) I think you patch reduces the readability a little although the idr code
   itself is already shit.
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