From 6daf14140129d30207ed6a0a69851fa6a3636bda Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Thu, 20 Feb 2020 07:59:14 -0600 Subject: netfilter: Replace zero-length array with flexible-array member The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on. Also, notice that, dynamic memory allocations won't be affected by this change: "Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1] Lastly, fix checkpatch.pl warning WARNING: __aligned(size) is preferred over __attribute__((aligned(size))) in net/bridge/netfilter/ebtables.c This issue was found with the help of Coccinelle. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva Signed-off-by: Pablo Neira Ayuso --- include/net/netfilter/nf_conntrack_extend.h | 2 +- include/net/netfilter/nf_conntrack_timeout.h | 2 +- include/net/netfilter/nf_tables.h | 6 +++--- 3 files changed, 5 insertions(+), 5 deletions(-) (limited to 'include/net/netfilter') diff --git a/include/net/netfilter/nf_conntrack_extend.h b/include/net/netfilter/nf_conntrack_extend.h index 5ae5295aa46d..e1e588387103 100644 --- a/include/net/netfilter/nf_conntrack_extend.h +++ b/include/net/netfilter/nf_conntrack_extend.h @@ -45,7 +45,7 @@ enum nf_ct_ext_id { struct nf_ct_ext { u8 offset[NF_CT_EXT_NUM]; u8 len; - char data[0]; + char data[]; }; static inline bool __nf_ct_ext_exist(const struct nf_ct_ext *ext, u8 id) diff --git a/include/net/netfilter/nf_conntrack_timeout.h b/include/net/netfilter/nf_conntrack_timeout.h index 6dd72396f534..659b0ea25b4d 100644 --- a/include/net/netfilter/nf_conntrack_timeout.h +++ b/include/net/netfilter/nf_conntrack_timeout.h @@ -14,7 +14,7 @@ struct nf_ct_timeout { __u16 l3num; const struct nf_conntrack_l4proto *l4proto; - char data[0]; + char data[]; }; struct ctnl_timeout { diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h index d913cdb6a27b..01f48b5e6bf2 100644 --- a/include/net/netfilter/nf_tables.h +++ b/include/net/netfilter/nf_tables.h @@ -224,7 +224,7 @@ int nft_validate_register_store(const struct nft_ctx *ctx, */ struct nft_userdata { u8 len; - unsigned char data[0]; + unsigned char data[]; }; /** @@ -565,7 +565,7 @@ struct nft_set_ext_tmpl { struct nft_set_ext { u8 genmask; u8 offset[NFT_SET_EXT_NUM]; - char data[0]; + char data[]; }; static inline void nft_set_ext_prepare(struct nft_set_ext_tmpl *tmpl) @@ -1375,7 +1375,7 @@ struct nft_trans { int msg_type; bool put_net; struct nft_ctx ctx; - char data[0]; + char data[]; }; struct nft_trans_rule { -- cgit v1.2.3