From: Gustavo A. R. Silva Date: Mon, 17 Feb 2020 20:05:00 +0000 (-0600) Subject: svcrdma: Replace zero-length array with flexible-array member X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=c0fb23f867b632293500d7900e0288cf17bfcb1a;p=linux.git svcrdma: 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: J. Bruce Fields Signed-off-by: Chuck Lever --- diff --git a/net/sunrpc/xprtrdma/svc_rdma_rw.c b/net/sunrpc/xprtrdma/svc_rdma_rw.c index 48fe3b16b0d9c..003610ce00bc1 100644 --- a/net/sunrpc/xprtrdma/svc_rdma_rw.c +++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c @@ -41,7 +41,7 @@ struct svc_rdma_rw_ctxt { struct rdma_rw_ctx rw_ctx; int rw_nents; struct sg_table rw_sg_table; - struct scatterlist rw_first_sgl[0]; + struct scatterlist rw_first_sgl[]; }; static inline struct svc_rdma_rw_ctxt *