Re: [PATCH 0/4] clean up zero-length arrays

[Stephen Hemminger <stephen@networkplumber.org>]

On Thu,  2 Jun 2022 16:08:30 +0100
Bruce Richardson <bruce.richardson@intel.com> wrote:

> This patchset adds a coccinelle script to clean-up zero-length
> arrays in structures. The final patches are the result of running
> that script on the DPDK repository.
> 
> Bruce Richardson (4):
>   cocci: add script for zero-length arrays in structs
>   drivers: replace zero-length arrays with undimensioned ones
>   lib: replace zero-length arrays with undimensioned ones
>   app: examples: replace zero-length arrays with undimensioned ones
> 
>  app/test/test_table_tables.c                  |  2 +-
>  devtools/cocci/zero_length_array.cocci        | 21 +++++++++++++++
>  drivers/bus/dpaa/include/netcfg.h             |  4 +--
>  drivers/bus/vmbus/rte_vmbus_reg.h             |  4 +--
>  drivers/common/cnxk/roc_se.h                  |  2 +-
>  drivers/common/dpaax/caamflib/desc/ipsec.h    |  2 +-
>  drivers/common/dpaax/dpaax_iova_table.h       |  2 +-
>  drivers/common/mlx5/mlx5_prm.h                | 10 +++----
>  drivers/crypto/ipsec_mb/ipsec_mb_private.h    |  4 +--
>  drivers/crypto/virtio/virtio_ring.h           |  4 +--
>  drivers/crypto/virtio/virtqueue.h             |  2 +-
>  drivers/net/atlantic/hw_atl/hw_atl_utils.h    |  2 +-
>  drivers/net/cxgbe/clip_tbl.h                  |  2 +-
>  drivers/net/cxgbe/l2t.h                       |  2 +-
>  drivers/net/cxgbe/mps_tcam.h                  |  2 +-
>  drivers/net/cxgbe/smt.h                       |  2 +-
>  drivers/net/enic/base/vnic_devcmd.h           |  2 +-
>  drivers/net/hinic/hinic_pmd_tx.h              |  2 +-
>  drivers/net/mlx5/mlx5_tx.h                    |  2 +-
>  drivers/net/nfp/nfpcore/nfp_nsp.h             |  2 +-
>  drivers/net/virtio/virtio_ring.h              |  4 +--
>  drivers/net/virtio/virtio_user/vhost_kernel.c |  2 +-
>  drivers/net/virtio/virtio_user/vhost_vdpa.c   |  2 +-
>  drivers/net/virtio/virtqueue.h                |  2 +-
>  drivers/regex/mlx5/mlx5_rxp.h                 |  4 +--
>  examples/ip_reassembly/main.c                 |  2 +-
>  examples/ptpclient/ptpclient.c                |  4 +--
>  lib/cryptodev/cryptodev_pmd.h                 |  2 +-
>  lib/cryptodev/rte_cryptodev.h                 |  2 +-
>  lib/eventdev/rte_event_timer_adapter.h        |  2 +-
>  lib/ip_frag/ip_reassembly.h                   |  2 +-
>  lib/ipsec/sa.h                                |  2 +-
>  lib/rib/rte_rib.c                             |  2 +-
>  lib/rib/rte_rib6.c                            |  2 +-
>  lib/table/rte_swx_table_learner.c             |  4 +--
>  lib/table/rte_table_hash_key16.c              |  4 +--
>  lib/table/rte_table_hash_key32.c              |  4 +--
>  lib/table/rte_table_hash_key8.c               |  4 +--
>  lib/vhost/rte_vhost.h                         |  4 +--
>  40 files changed, 101 insertions(+), 54 deletions(-)
>  create mode 100644 devtools/cocci/zero_length_array.cocci
>  create mode 100644 lib/count_comments.py
> 
> --
> 2.34.1
> 

Bruce, looking at this commit, it looks like the underlying cause
of the problem with iavf was it is using array size of one
when flex array should be used:

commit b5b3ea803e4741ad6a46a38d8227c78226d9054d
Author: Kevin Traynor <ktraynor@redhat.com>
Date:   Fri Apr 17 16:43:35 2020 +0100

    eal/x86: ignore gcc 10 stringop-overflow warnings
    
    stringop-overflow warns when it sees a possible overflow
    in a string operation.
    
    In the rte_memcpy functions different branches are taken
    depending on the size. stringop-overflow is raised for the
    branches in the function where it sees the static size of the
    src could be overflowed.
    
    However, in reality a correct size argument and in some cases
    dynamic allocation would ensure that this does not happen.
    
    For example, in the case below for key, the correct path will be
    chosen in rte_memcpy_generic at runtime based on the size argument
    but as some paths in the function could lead to a cast to 32 bytes
    a warning is raised.
    
    In function ‘_mm256_storeu_si256’,
    inlined from ‘rte_memcpy_generic’
    at ../lib/librte_eal/common/include/arch/x86/rte_memcpy.h:315:2,
    inlined from ‘iavf_configure_rss_key’
    at ../lib/librte_eal/common/include/arch/x86/rte_memcpy.h:869:10:
    
    /usr/lib/gcc/x86_64-redhat-linux/10/include/avxintrin.h:928:8:
    warning: writing 32 bytes into a region of size 1 [-Wstringop-overflow=]
      928 |   *__P = __A;
          |   ~~~~~^~~~~
    In file included
    from ../drivers/net/iavf/../../common/iavf/iavf_prototype.h:10,
    from ../drivers/net/iavf/iavf.h:9,
    from ../drivers/net/iavf/iavf_vchnl.c:22:
    
    ../drivers/net/iavf/iavf_vchnl.c:
    In function ‘iavf_configure_rss_key’:
    
    ../drivers/net/iavf/../../common/iavf/virtchnl.h:508:5:
    note: at offset 0 to object ‘key’ with size 1 declared here
      508 |  u8 key[1];         /* RSS hash key, packed bytes */
          |     ^~~
    
    Ignore the stringop-overflow warnings for rte_memcpy.h functions.
    
    Bugzilla ID: 394
    Bugzilla ID: 421
    Cc: stable@dpdk.org
    
    Signed-off-by: Kevin Traynor <ktraynor@redhat.com>
    Acked-by: Bruce Richardson <bruce.richardson@intel.com>
    Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>