linux-kernel - Re: [PATCH][next] net: cisco: Replace zero-length array with flexible-array member

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20200226.164642.670797289411682529.davem@davemloft.net>
Date:   Wed, 26 Feb 2020 16:46:42 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     gustavo@...eddedor.com
Cc:     benve@...co.com, _govind@....com, pkaustub@...co.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] net: cisco: Replace zero-length array with
 flexible-array member

From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Date: Mon, 24 Feb 2020 18:18:26 -0600

> 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]
> 
> Lastly, fix the following checkpatch warning:
> CHECK: Prefer kernel type 'u32' over 'u_int32_t'
> #61: FILE: drivers/net/ethernet/cisco/enic/vnic_devcmd.h:653:
> +	u_int32_t val[];
> 
> 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 <gustavo@...eddedor.com>

Applied.