From: Gustavo A. R. Silva Date: Sat, 29 Feb 2020 00:50:23 +0000 (-0600) Subject: net: lwtunnel: Replace zero-length array with flexible-array member X-Git-Url: http://git.osdn.net/view?a=commitdiff_plain;h=e8316026d538873f60f41dab4caaa493a21684b0;p=uclinux-h8%2Flinux.git net: lwtunnel: 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] 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: David S. Miller --- diff --git a/include/net/lwtunnel.h b/include/net/lwtunnel.h index 5d6c5b1fc695..b5e6edf74b70 100644 --- a/include/net/lwtunnel.h +++ b/include/net/lwtunnel.h @@ -30,7 +30,7 @@ struct lwtunnel_state { int (*orig_output)(struct net *net, struct sock *sk, struct sk_buff *skb); int (*orig_input)(struct sk_buff *); struct rcu_head rcu; - __u8 data[0]; + __u8 data[]; }; struct lwtunnel_encap_ops {