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SubjectRe: [PATCH] ipv6: ioam: Replace 0-length array with flexible array
On Thu, Jan 05, 2023 at 02:21:16PM -0800, Kees Cook wrote:
> Zero-length arrays are deprecated[1]. Replace struct ioam6_trace_hdr's
> "data" 0-length array with a flexible array. Detected with GCC 13,
> using -fstrict-flex-arrays=3:
>
> net/ipv6/ioam6_iptunnel.c: In function 'ioam6_build_state':
> net/ipv6/ioam6_iptunnel.c:194:37: warning: array subscript <unknown> is outside array bounds of '__u8[0]' {aka 'unsigned char[]'} [-Warray-bounds=]
> 194 | tuninfo->traceh.data[trace->remlen * 4] = IPV6_TLV_PADN;
> | ~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~
> In file included from include/linux/ioam6.h:11,
> from net/ipv6/ioam6_iptunnel.c:13:
> include/uapi/linux/ioam6.h:130:17: note: while referencing 'data'
> 130 | __u8 data[0];
> | ^~~~
>
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays
>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: Justin Iurman <justin.iurman@uliege.be>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Paolo Abeni <pabeni@redhat.com>
> Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
> Cc: netdev@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks!
--
Gustavo

> ---
> include/uapi/linux/ioam6.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/ioam6.h b/include/uapi/linux/ioam6.h
> index ac4de376f0ce..8f72b24fefb3 100644
> --- a/include/uapi/linux/ioam6.h
> +++ b/include/uapi/linux/ioam6.h
> @@ -127,7 +127,7 @@ struct ioam6_trace_hdr {
> #endif
>
> #define IOAM6_TRACE_DATA_SIZE_MAX 244
> - __u8 data[0];
> + __u8 data[];
> } __attribute__((packed));
>
> #endif /* _UAPI_LINUX_IOAM6_H */
> --
> 2.34.1
>

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