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Re: [kernel-hardening] [PATCH 17/23] dcache: define usercopy region in dentry_cache slab cache

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On Mon, Jun 19, 2017 at 9:08 PM, Eric Biggers <ebiggers3@gmail.com> wrote:
> On Mon, Jun 19, 2017 at 04:36:31PM -0700, Kees Cook wrote:
>> From: David Windsor <dave@nullcore.net>
>>
>> When a dentry name is short enough, it can be stored directly in
>> the dentry itself.  These dentry short names, stored in struct
>> dentry.d_iname and therefore contained in the dentry_cache slab cache,
>> need to be coped to/from userspace.
>>
>> In support of usercopy hardening, this patch defines a region in
>> the dentry_cache slab cache in which userspace copy operations
>> are allowed.
>>
>> This region is known as the slab cache's usercopy region.  Slab
>> caches can now check that each copy operation involving cache-managed
>> memory falls entirely within the slab's usercopy region.
>>
>> This patch is modified from Brad Spengler/PaX Team's PAX_USERCOPY
>> whitelisting code in the last public patch of grsecurity/PaX based on my
>> understanding of the code. Changes or omissions from the original code are
>> mine and don't reflect the original grsecurity/PaX code.
>>
>
> For all these patches please mention *where* the data is being copied to/from
> userspace.

Can you explain what you mean here? The field being copied is already
mentioned in the commit log; do you mean where in the kernel source
does the copy happen?

>
>> diff --git a/include/linux/slab.h b/include/linux/slab.h
>> index a48f54238273..97f4a0117b3b 100644
>> --- a/include/linux/slab.h
>> +++ b/include/linux/slab.h
>> @@ -151,6 +151,11 @@ void memcg_destroy_kmem_caches(struct mem_cgroup *);
>>               sizeof(struct __struct), __alignof__(struct __struct),\
>>               (__flags), NULL)
>>
>> +#define KMEM_CACHE_USERCOPY(__struct, __flags, __field) kmem_cache_create_usercopy(#__struct,\
>> +             sizeof(struct __struct), __alignof__(struct __struct),\
>> +             (__flags), offsetof(struct __struct, __field),\
>> +             sizeof_field(struct __struct, __field), NULL)
>> +
>
> This helper macro should be added in the patch which adds
> kmem_cache_create_usercopy(), not in this one.

It got moved here since this was the only user of this function and
there was already enough happening in the first patch. But yes,
probably it should stay with the first patch. It can be moved.

-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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