From: Gustavo A. R. Silva Date: Fri, 28 Feb 2020 13:23:23 +0000 (-0600) Subject: sunrpc: Replace zero-length array with flexible-array member X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=469aef23aa4e49d5191050410a1422117db03e11;p=linux.git sunrpc: 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/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h index 1afe38eb33f7e..7f0a83451bc02 100644 --- a/include/linux/sunrpc/svc.h +++ b/include/linux/sunrpc/svc.h @@ -380,7 +380,7 @@ struct svc_deferred_req { struct cache_deferred_req handle; size_t xprt_hlen; int argslen; - __be32 args[0]; + __be32 args[]; }; struct svc_process_info {