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    SubjectRe: [PATCH v3] ethtool: Replace 0-length array with flexible array
    On Fri. 6 Jan 2023 at 13:28, Kees Cook <keescook@chromium.org> wrote:
    > Zero-length arrays are deprecated[1]. Replace struct ethtool_rxnfc's
    > "rule_locs" 0-length array with a flexible array. Detected with GCC 13,
    > using -fstrict-flex-arrays=3:
    >
    > net/ethtool/common.c: In function 'ethtool_get_max_rxnfc_channel':
    > net/ethtool/common.c:558:55: warning: array subscript i is outside array bounds of '__u32[0]' {aka 'unsigned int[]'} [-Warray-bounds=]
    > 558 | .fs.location = info->rule_locs[i],
    > | ~~~~~~~~~~~~~~~^~~
    > In file included from include/linux/ethtool.h:19,
    > from include/uapi/linux/ethtool_netlink.h:12,
    > from include/linux/ethtool_netlink.h:6,
    > from net/ethtool/common.c:3:
    > include/uapi/linux/ethtool.h:1186:41: note: while referencing
    > 'rule_locs'
    > 1186 | __u32 rule_locs[0];
    > | ^~~~~~~~~
    >
    > [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays

    Side comment, this link does not mention the __DECLARE_FLEX_ARRAY().
    It could be good to add a reference to the helper here. But of course,
    this is not a criticism of this patch.

    > Cc: "David S. Miller" <davem@davemloft.net>
    > Cc: Jakub Kicinski <kuba@kernel.org>
    > Cc: Andrew Lunn <andrew@lunn.ch>
    > Cc: kernel test robot <lkp@intel.com>
    > Cc: Oleksij Rempel <linux@rempel-privat.de>
    > Cc: Sean Anderson <sean.anderson@seco.com>
    > Cc: Alexandru Tachici <alexandru.tachici@analog.com>
    > Cc: Amit Cohen <amcohen@nvidia.com>
    > Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
    > Cc: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
    > Cc: netdev@vger.kernel.org
    > Signed-off-by: Kees Cook <keescook@chromium.org>

    Reviewed-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>

    > ---
    > v3: don't use helper (vincent)

    You may want to double check your other patches as well. At least this
    one is also using the helper when not needed:

    https://lore.kernel.org/netdev/20230105223642.never.980-kees@kernel.org/T/#u

    > v2: https://lore.kernel.org/lkml/20230105233420.gonna.036-kees@kernel.org
    > ---
    > include/uapi/linux/ethtool.h | 2 +-
    > 1 file changed, 1 insertion(+), 1 deletion(-)
    >
    > diff --git a/include/uapi/linux/ethtool.h b/include/uapi/linux/ethtool.h
    > index 58e587ba0450..3135fa0ba9a4 100644
    > --- a/include/uapi/linux/ethtool.h
    > +++ b/include/uapi/linux/ethtool.h
    > @@ -1183,7 +1183,7 @@ struct ethtool_rxnfc {
    > __u32 rule_cnt;
    > __u32 rss_context;
    > };
    > - __u32 rule_locs[0];
    > + __u32 rule_locs[];
    > };
    >
    >
    > --
    > 2.34.1
    >

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