linux-kernel - Re: [PATCH] slub/slab: fix kmemleak didn't work on some case

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Message-ID: <alpine.DEB.2.11.1506080425350.10651@east.gentwo.org>
Date:	Mon, 8 Jun 2015 04:38:13 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	"Liu, XinwuX" <xinwux.liu@...el.com>
cc:	"catalin.marinas@....com" <catalin.marinas@....com>,
	"penberg@...nel.org" <penberg@...nel.org>,
	"mpm@...enic.com" <mpm@...enic.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"yanmin_zhang@...ux.intel.com" <yanmin_zhang@...ux.intel.com>,
	"He, Bo" <bo.he@...el.com>, "Chen, Lin Z" <lin.z.chen@...el.com>
Subject: Re: [PATCH] slub/slab: fix kmemleak didn't work on some case

On Mon, 8 Jun 2015, Liu, XinwuX wrote:

> when kernel uses kmalloc to allocate memory, slub/slab will find
> a suitable kmem_cache. Ususally the cache's object size is often
> greater than requested size. There is unused space which contains
> dirty data. These dirty data might have pointers pointing to a block

dirty? In what sense?

> of leaked memory. Kernel wouldn't consider this memory as leaked when
> scanning kmemleak object.

This has never been considered leaked memory before to my knowledge and
the data is already initialized.

F.e. The zeroing function in linux/mm/slub.c::slab_alloc_node() zeros the
complete object and not only the number of bytes specified in the kmalloc
call. Same thing is true for SLAB.

I am a bit confused as to what issue this patch would address.

Also please send clean patches without special characters. Ensure proper
tabbing etc.

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