From b0c9a2d9a8ee13ec68ff5f80fdd74bd83272f967 Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Fri, 28 Feb 2020 07:36:41 -0600 Subject: ipv6: 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 --- net/ipv6/ah6.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'net/ipv6/ah6.c') diff --git a/net/ipv6/ah6.c b/net/ipv6/ah6.c index 95835e8d99aa..871d6e52ec67 100644 --- a/net/ipv6/ah6.c +++ b/net/ipv6/ah6.c @@ -36,7 +36,7 @@ struct tmp_ext { struct in6_addr saddr; #endif struct in6_addr daddr; - char hdrs[0]; + char hdrs[]; }; struct ah_skb_cb { -- cgit v1.2.3