From 0f74226649fb2875a91b68f3750f55220aa73425 Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Thu, 13 Feb 2020 09:14:09 -0600 Subject: [PATCH] kernel: module: 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: Jessica Yu --- kernel/module.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/module.c b/kernel/module.c index 33569a01d6e1..b88ec9cd2a7f 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -1515,7 +1515,7 @@ struct module_sect_attr { struct module_sect_attrs { struct attribute_group grp; unsigned int nsections; - struct module_sect_attr attrs[0]; + struct module_sect_attr attrs[]; }; static ssize_t module_sect_show(struct module_attribute *mattr, @@ -1608,7 +1608,7 @@ static void remove_sect_attrs(struct module *mod) struct module_notes_attrs { struct kobject *dir; unsigned int notes; - struct bin_attribute attrs[0]; + struct bin_attribute attrs[]; }; static ssize_t module_notes_read(struct file *filp, struct kobject *kobj,