[PATCH] ipv6: ioam: Replace 0-length array with flexible array

[PATCH] ipv6: ioam: Replace 0-length array with flexible array

[Kees Cook]

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>
---
 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

Re: [PATCH] ipv6: ioam: Replace 0-length array with flexible array

[Gustavo A. R. Silva]

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
> 

Re: [PATCH] ipv6: ioam: Replace 0-length array with flexible array

[Justin Iurman]

On 1/5/23 23:21, 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: Justin Iurman <justin.iurman@uliege.be>
Tested-by: Justin Iurman <justin.iurman@uliege.be>

LGTM, thanks.

> ---
>   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 */

Re: [PATCH] ipv6: ioam: Replace 0-length array with flexible array

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Thu,  5 Jan 2023 14:21:16 -0800 you 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];
>       |                 ^~~~
> 
> [...]

Here is the summary with links:
  - ipv6: ioam: Replace 0-length array with flexible array
    https://git.kernel.org/netdev/net-next/c/0b5dfa35da03

You are awesome, thank you!
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