linux-kernel - Re: [PATCH 0/5] kstrdup optimization

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Date:	Tue, 13 Jan 2015 16:10:57 -0800
From:	Craig Milo Rogers <rogers@....edu>
To:	Andrzej Hajda <a.hajda@...sung.com>
Cc:	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Linux MM <linux-mm@...ck.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>, Andreas Mohr <andi@...as.de>,
	Mike Turquette <mturquette@...aro.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 0/5] kstrdup optimization

> As kfree_const() has the exact same signature as kfree(), the risk of
> accidentally passing pointers returned from kstrdup_const() to kfree() seems
> high, which may lead to memory corruption if the pointer doesn't point to
> allocated memory.
...
>> To verify if the source is in .rodata function checks if the address is between
>> sentinels __start_rodata, __end_rodata. I guess it should work with all
>> architectures.

	kfree() could also check if the region being freed is in .rodata, and
ignore the call; kfree_const() would not be needed.  If making this check all
the time leads to a significant decrease in performance (numbers needed here),
another option is to keep kfree_const() but add a check to kfree(), when
compiled for debugging, that issues a suitable complaint if the region being
freed is in .rodata.

					Craig Milo Rogers
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