linux-kernel - Re: [PATCH 0/5] mm/slub: Improve data handling of krealloc() when orig

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Message-ID: <Zt+s2J87hZ7CZjl9@feng-clx.sh.intel.com>
Date: Tue, 10 Sep 2024 10:20:08 +0800
From: Feng Tang <feng.tang@...el.com>
To: Vlastimil Babka <vbabka@...e.cz>
CC: Andrew Morton <akpm@...ux-foundation.org>, Christoph Lameter
	<cl@...ux.com>, Pekka Enberg <penberg@...nel.org>, David Rientjes
	<rientjes@...gle.com>, Joonsoo Kim <iamjoonsoo.kim@....com>, Roman Gushchin
	<roman.gushchin@...ux.dev>, Hyeonggon Yoo <42.hyeyoo@...il.com>, "Andrey
 Konovalov" <andreyknvl@...il.com>, Marco Elver <elver@...gle.com>, Shuah Khan
	<skhan@...uxfoundation.org>, David Gow <davidgow@...gle.com>, "Danilo
 Krummrich" <dakr@...nel.org>, <linux-mm@...ck.org>,
	<kasan-dev@...glegroups.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/5] mm/slub: Improve data handling of krealloc() when
 orig_size is enabled

On Mon, Sep 09, 2024 at 07:12:31PM +0200, Vlastimil Babka wrote:
> On 9/9/24 03:29, Feng Tang wrote:
> > Danilo Krummrich's patch [1] raised one problem about krealloc() that
> > its caller doesn't know what's the actual request size, say the object
> > is 64 bytes kmalloc one, but the original caller may only requested 48
> > bytes. And when krealloc() shrinks or grows in the same object, or
> > allocate a new bigger object, it lacks this 'original size' information
> > to do accurate data preserving or zeroing (when __GFP_ZERO is set).
> > 
> > And when some slub debug option is enabled, kmalloc caches do have this
> > 'orig_size' feature. As suggested by Vlastimil, utilize it to do more
> > accurate data handling, as well as enforce the kmalloc-redzone sanity check.
> > 
> > To make the 'orig_size' accurate, we adjust some kasan/slub meta data
> > handling. Also add a slub kunit test case for krealloc().
> > 
> > This patchset has dependency over patches in both -mm tree and -slab
> > trees, so it is written based on linux-next tree '20240905' version.
> 
> Thanks, given the timing with merge window opening soon, I would take this
> into the slab tree after the merge window, when the current -next becomes
> 6.12-rc1.
 
Sounds good to me. Thanks for the review!

- Feng

> > 
> > [1]. https://lore.kernel.org/lkml/20240812223707.32049-1-dakr@kernel.org/
> > 
> > Thanks,
> > Feng
> > 
> > Feng Tang (5):
> >   mm/kasan: Don't store metadata inside kmalloc object when
> >     slub_debug_orig_size is on
> >   mm/slub: Consider kfence case for get_orig_size()
> >   mm/slub: Improve redzone check and zeroing for krealloc()
> >   kunit: kfence: Make KFENCE_TEST_REQUIRES macro available for all kunit
> >     case
> >   mm/slub, kunit: Add testcase for krealloc redzone and zeroing
> > 
> >  include/kunit/test.h    |   6 ++
> >  lib/slub_kunit.c        |  46 +++++++++++++++
> >  mm/kasan/generic.c      |   5 +-
> >  mm/kfence/kfence_test.c |   9 +--
> >  mm/slab.h               |   6 ++
> >  mm/slab_common.c        |  84 ---------------------------
> >  mm/slub.c               | 125 ++++++++++++++++++++++++++++++++++------
> >  7 files changed, 171 insertions(+), 110 deletions(-)
> > 
>