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Re: [kernel-hardening] Re: [PATCH v3 03/31] usercopy: Mark kmalloc caches as usercopy caches

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On Thu, Sep 21, 2017 at 9:04 AM, Christopher Lameter <cl@linux.com> wrote:
> On Thu, 21 Sep 2017, Kees Cook wrote:
>
>> > So what is the point of this patch?
>>
>> The DMA kmalloc caches are not whitelisted:
>
> The DMA kmalloc caches are pretty obsolete and mostly there for obscure
> drivers.
>
> ??

They may be obsolete, but they're still in the kernel, and they aren't
copied to userspace, so we can mark them.

>> >>                         kmalloc_dma_caches[i] = create_kmalloc_cache(n,
>> >> -                               size, SLAB_CACHE_DMA | flags);
>> >> +                               size, SLAB_CACHE_DMA | flags, 0, 0);
>>
>> So this is creating the distinction between the kmallocs that go to
>> userspace and those that don't. The expectation is that future work
>> can start to distinguish between "for userspace" and "only kernel"
>> kmalloc allocations, as is already done here for DMA.
>
> The creation of the kmalloc caches in earlier patches already setup the
> "whitelisting". Why do it twice?

Patch 1 is to allow for things to mark their whitelists. Patch 30
disables the full whitelisting, since then we've defined them all, so
the kmalloc caches need to mark themselves as whitelisted.

Patch 1 leaves unmarked things whitelisted so we can progressively
tighten the restriction and have a bisectable series. (i.e. if there
is something wrong with one of the whitelists in the series, it will
bisect to that one, not the one that removes the global whitelist from
patch 1.)

-Kees

-- 
Kees Cook
Pixel Security

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[PATCH v3 00/31] Hardened usercopy whitelisting Kees Cook <keescook@chromium.org> - 2017-09-20 22:50 +0200
  [PATCH v3 26/31] fork: Provide usercopy whitelisting for task_struct Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
  [PATCH v3 15/31] xfs: Define usercopy region in xfs_inode slab cache Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
  [PATCH v3 07/31] ext4: Define usercopy region in ext4_inode_cache slab cache Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
  [PATCH v3 29/31] arm: Implement thread_struct whitelist for hardened usercopy Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
  [PATCH v3 25/31] fork: Define usercopy region in thread_stack slab caches Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
  [PATCH v3 02/31] usercopy: Enforce slab cache usercopy region boundaries Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
    Re: [PATCH v3 02/31] usercopy: Enforce slab cache usercopy region  boundaries Christopher Lameter <cl@linux.com> - 2017-09-21 17:30 +0200
  [PATCH v3 23/31] net: Restrict unwhitelisted proto caches to size 0 Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
  [PATCH v3 17/31] scsi: Define usercopy region in scsi_sense_cache slab cache Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
  [PATCH v3 19/31] ip: Define usercopy region in IP proto slab cache Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
  [PATCH v3 28/31] arm64: Implement thread_struct whitelist for hardened usercopy Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
  [PATCH v3 21/31] sctp: Define usercopy region in SCTP proto slab cache Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
  [PATCH v3 31/31] lkdtm: Update usercopy tests for whitelisting Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
  [PATCH v3 01/31] usercopy: Prepare for usercopy whitelisting Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
    Re: [PATCH v3 01/31] usercopy: Prepare for usercopy whitelisting Christopher Lameter <cl@linux.com> - 2017-09-21 17:30 +0200
  [PATCH v3 08/31] ext2: Define usercopy region in ext2_inode_cache slab cache Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
  [PATCH v3 18/31] net: Define usercopy region in struct proto slab cache Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
  [PATCH v3 24/31] fork: Define usercopy region in mm_struct slab caches Kees Cook <keescook@chromium.org> - 2017-09-20 23:00 +0200
  [PATCH v3 04/31] dcache: Define usercopy region in dentry_cache slab cache Kees Cook <keescook@chromium.org> - 2017-09-20 23:10 +0200
  [PATCH v3 27/31] x86: Implement thread_struct whitelist for hardened usercopy Kees Cook <keescook@chromium.org> - 2017-09-20 23:10 +0200
  [PATCH v3 03/31] usercopy: Mark kmalloc caches as usercopy caches Kees Cook <keescook@chromium.org> - 2017-09-20 23:10 +0200
    Re: [PATCH v3 03/31] usercopy: Mark kmalloc caches as usercopy  caches Christopher Lameter <cl@linux.com> - 2017-09-21 17:30 +0200
      Re: [kernel-hardening] Re: [PATCH v3 03/31] usercopy: Mark kmalloc  caches as usercopy caches Kees Cook <keescook@chromium.org> - 2017-09-21 17:50 +0200
        Re: [kernel-hardening] Re: [PATCH v3 03/31] usercopy: Mark kmalloc  caches as usercopy caches Christopher Lameter <cl@linux.com> - 2017-09-21 18:10 +0200
          Re: [kernel-hardening] Re: [PATCH v3 03/31] usercopy: Mark kmalloc  caches as usercopy caches Kees Cook <keescook@chromium.org> - 2017-09-21 20:30 +0200

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