From 5b361328ca649534d721e4eae20c96ccbe702ce7 Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Wed, 12 Feb 2020 19:04:25 -0600 Subject: RDMA: 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") Link: https://lore.kernel.org/r/20200213010425.GA13068@embeddedor.com Signed-off-by: Gustavo A. R. Silva Signed-off-by: Jason Gunthorpe # added a few more --- drivers/infiniband/hw/mthca/mthca_memfree.c | 2 +- drivers/infiniband/hw/mthca/mthca_memfree.h | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) (limited to 'drivers/infiniband/hw/mthca') diff --git a/drivers/infiniband/hw/mthca/mthca_memfree.c b/drivers/infiniband/hw/mthca/mthca_memfree.c index 78a48aea3faf..fa808582b08b 100644 --- a/drivers/infiniband/hw/mthca/mthca_memfree.c +++ b/drivers/infiniband/hw/mthca/mthca_memfree.c @@ -58,7 +58,7 @@ struct mthca_user_db_table { u64 uvirt; struct scatterlist mem; int refcount; - } page[0]; + } page[]; }; static void mthca_free_icm_pages(struct mthca_dev *dev, struct mthca_icm_chunk *chunk) diff --git a/drivers/infiniband/hw/mthca/mthca_memfree.h b/drivers/infiniband/hw/mthca/mthca_memfree.h index da9b8f9b884f..f9a2e65e2ff5 100644 --- a/drivers/infiniband/hw/mthca/mthca_memfree.h +++ b/drivers/infiniband/hw/mthca/mthca_memfree.h @@ -68,7 +68,7 @@ struct mthca_icm_table { int lowmem; int coherent; struct mutex mutex; - struct mthca_icm *icm[0]; + struct mthca_icm *icm[]; }; struct mthca_icm_iter { -- cgit