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Re: [kernel-hardening] [PATCH 21/23] usercopy: Restrict non-usercopy caches to size 0

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On Mon, Jun 19, 2017 at 9:04 PM, Eric Biggers <ebiggers3@gmail.com> wrote:
> Hi David + Kees,
>
> On Mon, Jun 19, 2017 at 04:36:35PM -0700, Kees Cook wrote:
>> With all known usercopied cache whitelists now defined in the kernel, switch
>> the default usercopy region of kmem_cache_create() to size 0. Any new caches
>> with usercopy regions will now need to use kmem_cache_create_usercopy()
>> instead of kmem_cache_create().
>>
>
> While I'd certainly like to see the caches be whitelisted, it needs to be made
> very clear that it's being done (the cover letter for this series falsely claims
> that kmem_cache_create() is unchanged) and what the consequences are.  Is there

Well, in the first patch it is semantically unchanged: calls to
kmem_cache_create() after the first patch whitelist the entire cache
object. Only from this patch on does it change behavior to no longer
whitelist the object.

> any specific plan for identifying caches that were missed?  If it's expected for

The plan for finding caches needing whitelisting is mainly code audit
and operational testing. Encountering it is quite loud in that it BUGs
the kernel during the hardened usercopy checks.

> people to just fix them as they are found, then they need to be helped a little
> --- at the very least by putting a big comment above report_usercopy() that
> explains the possible reasons why the error might have triggered and what to do
> about it.

That sounds reasonable. It should have a comment even for the existing
protections.

Thanks!

-Kees

-- 
Kees Cook
Pixel Security

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[PATCH 00/23] Hardened usercopy whitelisting Kees Cook <keescook@chromium.org> - 2017-06-20 01:40 +0200
  [PATCH 13/23] ufs: define usercopy region in ufs_inode_cache slab cache Kees Cook <keescook@chromium.org> - 2017-06-20 01:40 +0200
  [PATCH 22/23] usercopy: split user-controlled slabs to separate caches Kees Cook <keescook@chromium.org> - 2017-06-20 01:40 +0200
    Re: [kernel-hardening] [PATCH 22/23] usercopy: split user-controlled  slabs to separate caches Eric Biggers <ebiggers3@gmail.com> - 2017-06-20 06:30 +0200
    Re: [kernel-hardening] [PATCH 22/23] usercopy: split user-controlled  slabs to separate caches Eric Biggers <ebiggers3@gmail.com> - 2017-06-20 06:50 +0200
      Re: [kernel-hardening] [PATCH 22/23] usercopy: split user-controlled  slabs to separate caches Kees Cook <keescook@chromium.org> - 2017-06-21 00:30 +0200
    Re: [PATCH 22/23] usercopy: split user-controlled slabs to separate  caches Laura Abbott <labbott@redhat.com> - 2017-06-20 22:30 +0200
      Re: [PATCH 22/23] usercopy: split user-controlled slabs to separate caches Kees Cook <keescook@chromium.org> - 2017-06-21 00:30 +0200
        Re: [PATCH 22/23] usercopy: split user-controlled slabs to separate  caches Michal Hocko <mhocko@kernel.org> - 2017-06-27 09:40 +0200
          Re: [PATCH 22/23] usercopy: split user-controlled slabs to separate caches Kees Cook <keescook@chromium.org> - 2017-06-28 00:10 +0200
            Re: [PATCH 22/23] usercopy: split user-controlled slabs to separate  caches Michal Hocko <mhocko@kernel.org> - 2017-06-28 11:00 +0200
  [PATCH 08/23] ext2: define usercopy region in ext2_inode_cache slab cache Kees Cook <keescook@chromium.org> - 2017-06-20 01:40 +0200
  [PATCH 15/23] net: define usercopy region in struct proto slab cache Kees Cook <keescook@chromium.org> - 2017-06-20 01:40 +0200
  [PATCH 14/23] fork: define usercopy region in thread_stack, task_struct, mm_struct slab caches Kees Cook <keescook@chromium.org> - 2017-06-20 01:40 +0200
  [PATCH 11/23] jfs: define usercopy region in jfs_ip slab cache Kees Cook <keescook@chromium.org> - 2017-06-20 01:40 +0200
  [PATCH 20/23] usercopy: convert kmalloc caches to usercopy caches Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
  [PATCH 05/23] befs: define usercopy region in befs_inode_cache slab cache Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
  [PATCH 23/23] mm: Allow slab_nomerge to be set at build time Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
    Re: [kernel-hardening] [PATCH 23/23] mm: Allow slab_nomerge to be  set at build time Daniel Micay <danielmicay@gmail.com> - 2017-06-20 06:10 +0200
      Re: [kernel-hardening] [PATCH 23/23] mm: Allow slab_nomerge to be set  at build time Kees Cook <keescook@chromium.org> - 2017-06-21 01:00 +0200
    Re: [kernel-hardening] [PATCH 23/23] mm: Allow slab_nomerge to be  set at build time Eric Biggers <ebiggers3@gmail.com> - 2017-06-20 06:30 +0200
      Re: [kernel-hardening] [PATCH 23/23] mm: Allow slab_nomerge to be set  at build time Kees Cook <keescook@chromium.org> - 2017-06-21 01:20 +0200
  [PATCH 19/23] xfs: define usercopy region in xfs_inode slab cache Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
  [PATCH 01/23] usercopy: Prepare for usercopy whitelisting Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
  [PATCH 03/23] vfs: define usercopy region in names_cache slab caches Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
  [PATCH 17/23] dcache: define usercopy region in dentry_cache slab cache Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
    Re: [kernel-hardening] [PATCH 17/23] dcache: define usercopy region  in dentry_cache slab cache Eric Biggers <ebiggers3@gmail.com> - 2017-06-20 06:10 +0200
      Re: [kernel-hardening] [PATCH 17/23] dcache: define usercopy region  in dentry_cache slab cache Eric Biggers <ebiggers3@gmail.com> - 2017-06-28 20:00 +0200
      Re: [kernel-hardening] [PATCH 17/23] dcache: define usercopy region  in dentry_cache slab cache Kees Cook <keescook@chromium.org> - 2017-06-28 20:00 +0200
  [PATCH 04/23] vfs: copy struct mount.mnt_id to userspace using put_user() Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
  [PATCH 06/23] cifs: define usercopy region in cifs_request slab cache Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
  [PATCH 21/23] usercopy: Restrict non-usercopy caches to size 0 Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
    Re: [kernel-hardening] [PATCH 21/23] usercopy: Restrict non-usercopy  caches to size 0 Eric Biggers <ebiggers3@gmail.com> - 2017-06-20 06:10 +0200
      Re: [kernel-hardening] [PATCH 21/23] usercopy: Restrict non-usercopy  caches to size 0 Kees Cook <keescook@chromium.org> - 2017-06-28 20:00 +0200
  [PATCH 18/23] scsi: define usercopy region in scsi_sense_cache slab cache Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
  [PATCH 02/23] usercopy: Enforce slab cache usercopy region boundaries Kees Cook <keescook@chromium.org> - 2017-06-20 01:50 +0200
  Re: [kernel-hardening] [PATCH 00/23] Hardened usercopy whitelisting Rik van Riel <riel@redhat.com> - 2017-06-20 21:50 +0200

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