[PATCH v2] ethtool: Replace 0-length array with flexible array

From: Kees Cook
Date: Thu Jan 05 2023 - 18:34:32 EST


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" <davem@xxxxxxxxxxxxx>
Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
Cc: Andrew Lunn <andrew@xxxxxxx>
Cc: kernel test robot <lkp@xxxxxxxxx>
Cc: Oleksij Rempel <linux@xxxxxxxxxxxxxxxx>
Cc: Sean Anderson <sean.anderson@xxxxxxxx>
Cc: Alexandru Tachici <alexandru.tachici@xxxxxxxxxx>
Cc: Amit Cohen <amcohen@xxxxxxxxxx>
Cc: "Gustavo A. R. Silva" <gustavoars@xxxxxxxxxx>
Cc: Vincent Mailhol <mailhol.vincent@xxxxxxxxxx>
Cc: netdev@xxxxxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
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