linux-kernel - Re: [PATCH] mm: Make ksize() a reporting-only function

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Date:   Tue, 25 Oct 2022 11:38:06 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Christoph Lameter <cl@...ux.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        linux-mm@...ck.org, kasan-dev@...glegroups.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH] mm: Make ksize() a reporting-only function

On Tue, Oct 25, 2022 at 01:53:54PM +0200, Vlastimil Babka wrote:
> On 10/22/22 20:08, Kees Cook wrote:
> > With all "silently resizing" callers of ksize() refactored, remove the
> > logic in ksize() that would allow it to be used to effectively change
> > the size of an allocation (bypassing __alloc_size hints, etc). Users
> > wanting this feature need to either use kmalloc_size_roundup() before an
> > allocation, or use krealloc() directly.
> > 
> > For kfree_sensitive(), move the unpoisoning logic inline. Replace the
> > some of the partially open-coded ksize() in __do_krealloc with ksize()
> > now that it doesn't perform unpoisoning.
> > 
> > [...]
> > Signed-off-by: Kees Cook <keescook@...omium.org>
> 
> Acked-by: Vlastimil Babka <vbabka@...e.cz>

Thanks!

> > ---
> > This requires at least this be landed first:
> > https://lore.kernel.org/lkml/20221021234713.you.031-kees@kernel.org/
> 
> Don't we need all parts to have landed first, even if the skbuff one is the
> most prominent?

Yes, though, I suspect there will be some cases we couldn't easily find.

Here are the prerequisites I'm aware of:

in -next:
  36875a063b5e ("net: ipa: Proactively round up to kmalloc bucket size")
  ab3f7828c979 ("openvswitch: Use kmalloc_size_roundup() to match ksize() usage")
  d6dd508080a3 ("bnx2: Use kmalloc_size_roundup() to match ksize() usage")

reviewed, waiting to land (should I take these myself?)
  btrfs: send: Proactively round up to kmalloc bucket size
    https://lore.kernel.org/lkml/20220923202822.2667581-8-keescook@chromium.org/
  dma-buf: Proactively round up to kmalloc bucket size
    https://lore.kernel.org/lkml/20221018090858.never.941-kees@kernel.org/

partially reviewed:
  igb: Proactively round up to kmalloc bucket size
    https://lore.kernel.org/lkml/20221018092340.never.556-kees@kernel.org/

unreviewed:
  coredump: Proactively round up to kmalloc bucket size
    https://lore.kernel.org/lkml/20221018090701.never.996-kees@kernel.org/
  devres: Use kmalloc_size_roundup() to match ksize() usage
    https://lore.kernel.org/lkml/20221018090406.never.856-kees@kernel.org/

needs updating:
  mempool: Use kmalloc_size_roundup() to match ksize() usage
    https://lore.kernel.org/lkml/20221018090323.never.897-kees@kernel.org/
  bpf: Use kmalloc_size_roundup() to match ksize() usage
    https://lore.kernel.org/lkml/20221018090550.never.834-kees@kernel.org/

-- 
Kees Cook