From 1a91a36aba9c232c73e4a5fce038147f5d29e566 Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Wed, 26 Feb 2020 16:31:25 -0600 Subject: mmc: 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 Acked-by: Adrian Hunter Link: https://lore.kernel.org/r/20200226223125.GA20630@embeddedor Signed-off-by: Ulf Hansson --- include/linux/mmc/host.h | 2 +- include/linux/mmc/sdio_func.h | 2 +- include/uapi/linux/mmc/ioctl.h | 2 +- 3 files changed, 3 insertions(+), 3 deletions(-) (limited to 'include') diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h index f5db24a6a860..c318fb5b6a94 100644 --- a/include/linux/mmc/host.h +++ b/include/linux/mmc/host.h @@ -468,7 +468,7 @@ struct mmc_host { /* Host Software Queue support */ bool hsq_enabled; - unsigned long private[0] ____cacheline_aligned; + unsigned long private[] ____cacheline_aligned; }; struct device_node; diff --git a/include/linux/mmc/sdio_func.h b/include/linux/mmc/sdio_func.h index 5a177f7a83c3..fa2aaab5e57a 100644 --- a/include/linux/mmc/sdio_func.h +++ b/include/linux/mmc/sdio_func.h @@ -25,7 +25,7 @@ struct sdio_func_tuple { struct sdio_func_tuple *next; unsigned char code; unsigned char size; - unsigned char data[0]; + unsigned char data[]; }; /* diff --git a/include/uapi/linux/mmc/ioctl.h b/include/uapi/linux/mmc/ioctl.h index 00c08120f3ba..98e29e7f54ac 100644 --- a/include/uapi/linux/mmc/ioctl.h +++ b/include/uapi/linux/mmc/ioctl.h @@ -57,7 +57,7 @@ struct mmc_ioc_cmd { */ struct mmc_ioc_multi_cmd { __u64 num_of_cmds; - struct mmc_ioc_cmd cmds[0]; + struct mmc_ioc_cmd cmds[]; }; #define MMC_IOC_CMD _IOWR(MMC_BLOCK_MAJOR, 0, struct mmc_ioc_cmd) -- cgit v1.2.3