Re: [PATCH 5/6] treewide: use kv[mz]alloc* rather than opencoded variants

[Kees Cook]

On Thu, Jan 12, 2017 at 7:37 AM, Michal Hocko <mhocko@xxxxxxxxxx> wrote:
> From: Michal Hocko <mhocko@xxxxxxxx>
>
> There are many code paths opencoding kvmalloc. Let's use the helper
> instead. The main difference to kvmalloc is that those users are usually
> not considering all the aspects of the memory allocator. E.g. allocation
> requests < 64kB are basically never failing and invoke OOM killer to
> satisfy the allocation. This sounds too disruptive for something that
> has a reasonable fallback - the vmalloc. On the other hand those
> requests might fallback to vmalloc even when the memory allocator would
> succeed after several more reclaim/compaction attempts previously. There
> is no guarantee something like that happens though.
>
> This patch converts many of those places to kv[mz]alloc* helpers because
> they are more conservative.
>
> Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
> Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
> Cc: Anton Vorontsov <anton@xxxxxxxxxx>
> Cc: Colin Cross <ccross@xxxxxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Tony Luck <tony.luck@xxxxxxxxx>
> Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
> Cc: Ben Skeggs <bskeggs@xxxxxxxxxx>
> Cc: Kent Overstreet <kent.overstreet@xxxxxxxxx>
> Cc: Santosh Raspatur <santosh@xxxxxxxxxxx>
> Cc: Hariprasad S <hariprasad@xxxxxxxxxxx>
> Cc: Tariq Toukan <tariqt@xxxxxxxxxxxx>
> Cc: Yishai Hadas <yishaih@xxxxxxxxxxxx>
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: Oleg Drokin <oleg.drokin@xxxxxxxxx>
> Cc: Andreas Dilger <andreas.dilger@xxxxxxxxx>
> Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Cc: David Sterba <dsterba@xxxxxxxx>
> Cc: "Yan, Zheng" <zyan@xxxxxxxxxx>
> Cc: Ilya Dryomov <idryomov@xxxxxxxxx>
> Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
> Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
> Cc: Eric Dumazet <eric.dumazet@xxxxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
>  arch/s390/kvm/kvm-s390.c                           | 10 ++-----
>  crypto/lzo.c                                       |  4 +--
>  drivers/acpi/apei/erst.c                           |  8 ++---
>  drivers/char/agp/generic.c                         |  8 +----
>  drivers/gpu/drm/nouveau/nouveau_gem.c              |  4 +--
>  drivers/md/bcache/util.h                           | 12 ++------
>  drivers/net/ethernet/chelsio/cxgb3/cxgb3_defs.h    |  3 --
>  drivers/net/ethernet/chelsio/cxgb3/cxgb3_offload.c | 25 ++--------------
>  drivers/net/ethernet/chelsio/cxgb3/l2t.c           |  2 +-
>  drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c    | 31 ++++----------------
>  drivers/net/ethernet/mellanox/mlx4/en_tx.c         |  9 ++----
>  drivers/net/ethernet/mellanox/mlx4/mr.c            |  9 ++----
>  drivers/nvdimm/dimm_devs.c                         |  5 +---
>  .../staging/lustre/lnet/libcfs/linux/linux-mem.c   | 11 +------
>  drivers/xen/evtchn.c                               | 14 +--------
>  fs/btrfs/ctree.c                                   |  9 ++----
>  fs/btrfs/ioctl.c                                   |  9 ++----
>  fs/btrfs/send.c                                    | 27 ++++++-----------
>  fs/ceph/file.c                                     |  9 ++----
>  fs/select.c                                        |  5 +---
>  fs/xattr.c                                         | 27 ++++++-----------
>  kernel/bpf/hashtab.c                               | 11 ++-----
>  lib/iov_iter.c                                     |  5 +---
>  mm/frame_vector.c                                  |  5 +---
>  net/ipv4/inet_hashtables.c                         |  6 +---
>  net/ipv4/tcp_metrics.c                             |  5 +---
>  net/mpls/af_mpls.c                                 |  5 +---
>  net/netfilter/x_tables.c                           | 34 ++++++----------------
>  net/netfilter/xt_recent.c                          |  5 +---
>  net/sched/sch_choke.c                              |  5 +---
>  net/sched/sch_fq_codel.c                           | 26 ++++-------------
>  net/sched/sch_hhf.c                                | 33 ++++++---------------
>  net/sched/sch_netem.c                              |  6 +---
>  net/sched/sch_sfq.c                                |  6 +---
>  security/keys/keyctl.c                             | 22 ++++----------
>  35 files changed, 96 insertions(+), 319 deletions(-)
>
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 4f74511015b8..e6bbb33d2956 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -1126,10 +1126,7 @@ static long kvm_s390_get_skeys(struct kvm *kvm, struct kvm_s390_skeys *args)
>         if (args->count < 1 || args->count > KVM_S390_SKEYS_MAX)
>                 return -EINVAL;
>
> -       keys = kmalloc_array(args->count, sizeof(uint8_t),
> -                            GFP_KERNEL | __GFP_NOWARN);
> -       if (!keys)
> -               keys = vmalloc(sizeof(uint8_t) * args->count);
> +       keys = kvmalloc(args->count * sizeof(uint8_t), GFP_KERNEL);

Before doing this conversion, can we add a kvmalloc_array() API? This
conversion could allow for the reintroduction of integer overflow
flaws. (This particular situation isn't at risk since ->count is
checked, but I'd prefer we not create a risky set of examples for
using kvmalloc.)

Besides that: yes please. Less open coding. :)

-Kees

-- 
Kees Cook
Nexus Security