From 2e83abdcb30e3881e9569fd8f4a600beef6cfadc Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Mon, 2 Mar 2020 06:00:48 -0600 Subject: net: mip6: 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 --- include/net/mip6.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/net/mip6.h') diff --git a/include/net/mip6.h b/include/net/mip6.h index f1c28971c362..67cd7e50804c 100644 --- a/include/net/mip6.h +++ b/include/net/mip6.h @@ -25,7 +25,7 @@ struct ip6_mh { __u8 ip6mh_reserved; __u16 ip6mh_cksum; /* Followed by type specific messages */ - __u8 data[0]; + __u8 data[]; } __packed; #define IP6_MH_TYPE_BRR 0 /* Binding Refresh Request */ -- cgit v1.2.3