From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To: Mimi Zohar <zohar@linux.ibm.com>,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
Roberto Sassu <roberto.sassu@huawei.com>,
Dmitry Kasatkin <dmitry.kasatkin@gmail.com>,
Eric Snowberg <eric.snowberg@oracle.com>,
Paul Moore <paul@paul-moore.com>,
James Morris <jmorris@namei.org>,
"Serge E. Hallyn" <serge@hallyn.com>
Cc: linux-integrity@vger.kernel.org,
linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH v3][next] integrity: Avoid -Wflex-array-member-not-at-end warnings
Date: Thu, 21 Mar 2024 09:49:29 -0600 [thread overview]
Message-ID: <afa0afb7-f756-45d0-97ab-44205e984199@embeddedor.com> (raw)
In-Reply-To: <267f340e1b309cff2fab01f83a141ee465296907.camel@linux.ibm.com>
On 3/21/24 07:58, Mimi Zohar wrote:
> On Wed, 2024-03-20 at 22:11 -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 an object (`hdr)` in `struct ima_max_digest_data`
>> that contains a flexible structure (`struct ima_digest_data`):
>>
>> struct ima_max_digest_data {
>> struct ima_digest_data hdr;
>> u8 digest[HASH_MAX_DIGESTSIZE];
>> } __packed;
>>
>> So, in order to avoid ending up with a flexible-array member in the
>> middle of a struct, we use the `__struct_group()` helper to separate
>> the flexible array from the rest of the members in the flexible
>> structure:
>>
>> struct ima_digest_data {
>> __struct_group(ima_digest_data_hdr, hdr, __packed,
>>
>> ... the rest of the members
>>
>> );
>> u8 digest[];
>> } __packed;
>>
>> With the change described above, we can now declare an object of the
>> type of the tagged `struct ima_digest_data_hdr`, without embedding the
>> flexible array in the middle of another struct:
>>
>> struct ima_max_digest_data {
>> struct ima_digest_data_hdr hdr;
>> u8 digest[HASH_MAX_DIGESTSIZE];
>> } __packed;
>>
>
> And similarly for 'struct evm_digest'.
Yes. :)
>
>
>> We also use `container_of()` whenever we need to retrieve a pointer to
>> the flexible structure.
>>
>> So, with these changes, fix the following warnings:
>>
>> security/integrity/evm/evm.h:45:32: warning: structure containing a flexible
>> array member is not at the end of another structure [-Wflex-array-member-not-
>> at-end]
>> security/integrity/evm/evm.h:45:32: warning: structure containing a flexible
>> array member is not at the end of another structure [-Wflex-array-member-not-
>> at-end]
>> security/integrity/evm/evm.h:45:32: warning: structure containing a flexible
>> array member is not at the end of another structure [-Wflex-array-member-not-
>> at-end]
>
> I assume these messages are gone.
Yes. :)
Thanks
--
Gustavo
prev parent reply other threads:[~2024-03-21 17:01 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-21 4:11 [PATCH v3][next] integrity: Avoid -Wflex-array-member-not-at-end warnings Gustavo A. R. Silva
2024-03-21 13:58 ` Mimi Zohar
2024-03-21 15:49 ` Gustavo A. R. Silva [this message]
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