From d2afb41ae60435cbe5d9d1078a7d90de04e571b8 Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Fri, 28 Feb 2020 07:43:24 -0600 Subject: net: core: 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/core/bpf_sk_storage.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'net/core/bpf_sk_storage.c') diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c index 3ab23f698221..427cfbc0d50d 100644 --- a/net/core/bpf_sk_storage.c +++ b/net/core/bpf_sk_storage.c @@ -60,7 +60,7 @@ struct bpf_sk_storage_data { * the number of cachelines access during the cache hit case. */ struct bpf_sk_storage_map __rcu *smap; - u8 data[0] __aligned(8); + u8 data[] __aligned(8); }; /* Linked to bpf_sk_storage and bpf_sk_storage_map */ -- cgit v1.2.3