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Re: [PATCH v3 02/31] usercopy: Enforce slab cache usercopy region boundaries

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On Wed, 20 Sep 2017, Kees Cook wrote:

> diff --git a/mm/slab.c b/mm/slab.c
> index 87b6e5e0cdaf..df268999cf02 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -4408,7 +4408,9 @@ module_init(slab_proc_init);
>
>  #ifdef CONFIG_HARDENED_USERCOPY
>  /*
> - * Rejects objects that are incorrectly sized.
> + * Rejects incorrectly sized objects and objects that are to be copied
> + * to/from userspace but do not fall entirely within the containing slab
> + * cache's usercopy region.
>   *
>   * Returns NULL if check passes, otherwise const char * to name of cache
>   * to indicate an error.
> @@ -4428,11 +4430,15 @@ const char *__check_heap_object(const void *ptr, unsigned long n,
>  	/* Find offset within object. */
>  	offset = ptr - index_to_obj(cachep, page, objnr) - obj_offset(cachep);
>
> -	/* Allow address range falling entirely within object size. */
> -	if (offset <= cachep->object_size && n <= cachep->object_size - offset)
> -		return NULL;
> +	/* Make sure object falls entirely within cache's usercopy region. */
> +	if (offset < cachep->useroffset)
> +		return cachep->name;
> +	if (offset - cachep->useroffset > cachep->usersize)
> +		return cachep->name;
> +	if (n > cachep->useroffset - offset + cachep->usersize)
> +		return cachep->name;
>
> -	return cachep->name;
> +	return NULL;
>  }
>  #endif /* CONFIG_HARDENED_USERCOPY */

Looks like this is almost the same for all allocators. Can we put this
into mm/slab_common.c?

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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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