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
Cc: "David S. Miller" <[email protected]>
Cc: Jakub Kicinski <[email protected]>
Cc: Andrew Lunn <[email protected]>
Cc: kernel test robot <[email protected]>
Cc: Oleksij Rempel <[email protected]>
Cc: Sean Anderson <[email protected]>
Cc: Alexandru Tachici <[email protected]>
Cc: Amit Cohen <[email protected]>
Cc: "Gustavo A. R. Silva" <[email protected]>
Cc: Vincent Mailhol <[email protected]>
Cc: [email protected]
Signed-off-by: Kees Cook <[email protected]>
---
v2: resend, this time without missing netdev CC. :)
---
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..9b97b3e0ec1f 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];
+ __DECLARE_FLEX_ARRAY(__u32, rule_locs);
};
--
2.34.1
On Fri. 6 Jan 2023 at 08:34, Kees Cook <[email protected]> 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
>
> Cc: "David S. Miller" <[email protected]>
> Cc: Jakub Kicinski <[email protected]>
> Cc: Andrew Lunn <[email protected]>
> Cc: kernel test robot <[email protected]>
> Cc: Oleksij Rempel <[email protected]>
> Cc: Sean Anderson <[email protected]>
> Cc: Alexandru Tachici <[email protected]>
> Cc: Amit Cohen <[email protected]>
> Cc: "Gustavo A. R. Silva" <[email protected]>
> Cc: Vincent Mailhol <[email protected]>
> Cc: [email protected]
> Signed-off-by: Kees Cook <[email protected]>
> ---
> v2: resend, this time without missing netdev CC. :)
> ---
> 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..9b97b3e0ec1f 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];
> + __DECLARE_FLEX_ARRAY(__u32, rule_locs);
Can't this simply be a C99 flexible array member?
__u32 rule_locs[];
As far as I understand, __DECLARE_FLEX_ARRAY() is a hack to allow the
declaration of a flexible array within unions (which otherwise do not
accept flexible array members). However, ethtool_rxnfc being a struct,
I do not see the need for __DECLARE_FLEX_ARRAY() here.
Yours sincerely,
Vincent Mailhol
On Fri, Jan 06, 2023 at 09:55:30AM +0900, Vincent MAILHOL wrote:
> On Fri. 6 Jan 2023 at 08:34, Kees Cook <[email protected]> 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
> >
> > Cc: "David S. Miller" <[email protected]>
> > Cc: Jakub Kicinski <[email protected]>
> > Cc: Andrew Lunn <[email protected]>
> > Cc: kernel test robot <[email protected]>
> > Cc: Oleksij Rempel <[email protected]>
> > Cc: Sean Anderson <[email protected]>
> > Cc: Alexandru Tachici <[email protected]>
> > Cc: Amit Cohen <[email protected]>
> > Cc: "Gustavo A. R. Silva" <[email protected]>
> > Cc: Vincent Mailhol <[email protected]>
> > Cc: [email protected]
> > Signed-off-by: Kees Cook <[email protected]>
> > ---
> > v2: resend, this time without missing netdev CC. :)
> > ---
> > 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..9b97b3e0ec1f 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];
> > + __DECLARE_FLEX_ARRAY(__u32, rule_locs);
>
> Can't this simply be a C99 flexible array member?
>
> __u32 rule_locs[];
>
> As far as I understand, __DECLARE_FLEX_ARRAY() is a hack to allow the
> declaration of a flexible array within unions (which otherwise do not
> accept flexible array members). However, ethtool_rxnfc being a struct,
> I do not see the need for __DECLARE_FLEX_ARRAY() here.
Good point -- I think my eyes scanned through the "union" above and I
just jumped at using __DECLARE_FLEX_ARRAY. I'll send a v2. Thanks!
--
Kees Cook