Received-SPF: pass (google.com: domain of linux-kernel+bounces-94179-linux.lists.archive=gmail.com@vger.kernel.org designates 139.178.88.99 as permitted sender) client-ip=139.178.88.99;
Message-ID: <34889a1a-4c8f-4c4d-865a-f947569f8d9c@embeddedor.com>
Date: Wed, 6 Mar 2024 09:42:50 -0600
Precedence: bulk
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH][next] fsnotify: Avoid -Wflex-array-member-not-at-end
 warning
Content-Language: en-US
To: Amir Goldstein <amir73il@gmail.com>, Kees Cook <keescook@chromium.org>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>, Jan Kara <jack@suse.cz>,
 Alexander Viro <viro@zeniv.linux.org.uk>,
 Christian Brauner <brauner@kernel.org>, linux-fsdevel@vger.kernel.org,
 linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
References: <ZeeaRuTpuxInH6ZB@neat> <202403051548.045B16BF@keescook>
 <CAOQ4uxg185+i+n_mnXsEaxXYJ1SseDH6RtGreTJDhjkOt6mmSA@mail.gmail.com>
From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
In-Reply-To: <CAOQ4uxg185+i+n_mnXsEaxXYJ1SseDH6RtGreTJDhjkOt6mmSA@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit


On 3/6/24 01:36, Amir Goldstein wrote:
> On Wed, Mar 6, 2024 at 1:52 AM Kees Cook <keescook@chromium.org> wrote:
>>
>> On Tue, Mar 05, 2024 at 04:18:46PM -0600, Gustavo A. R. Silva wrote:
>>> -Wflex-array-member-not-at-end is coming in GCC-14, and we are getting
>>> ready to enable it globally.
>>>
>>> There is currently a local structure `f` that is using a flexible
>>> `struct file_handle` as header for an on-stack place-holder for the
>>> flexible-array member `unsigned char f_handle[];`.
>>>
>>> struct {
>>>        struct file_handle handle;
>>>        u8 pad[MAX_HANDLE_SZ];
>>> } f;
>>
>> This code pattern is "put a flex array struct on the stack", but we have
>> a macro for this now:
>>
>> DEFINE_FLEX(struct file_handle, handle, f_handle, MAX_HANDLE_SZ);
>>
>> And you can even include the initializer:
>>
>> _DEFINE_FLEX(struct file_handle, handle, f_handle, MAX_HANDLE_SZ,
>>               = { .handle_bytes = MAX_HANDLE_SZ });
>>
> 
> Indeed that looks much nicer.


Yeah, I'll probably wait for this to land before I send a v2:

https://lore.kernel.org/linux-hardening/20240306010746.work.678-kees@kernel.org/

Thanks
--
Gustavo