Re: [PATCH 0/5] mm/slub: Improve data handling of krealloc() when orig_size is enabled

[Vlastimil Babka]

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.

> 
> [1]. https://lore.kernel.org/lkml/20240812223707.32049-1-dakr@xxxxxxxxxx/
> 
> 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(-)
>