linux-kernel - Re: [PATCH] crash_dump: Constify struct configfs_item_operations and configfs_group

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Message-ID: <b1c7b612-5c5e-4234-9aa5-a83105d01c52@wanadoo.fr>
Date: Mon, 15 Dec 2025 08:19:33 +0100
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Baoquan He <bhe@...hat.com>, coxu@...hat.com
Cc: Andrew Morton <akpm@...ux-foundation.org>, Vivek Goyal
 <vgoyal@...hat.com>, Dave Young <dyoung@...hat.com>,
 linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
 kexec@...ts.infradead.org
Subject: Re: [PATCH] crash_dump: Constify struct configfs_item_operations and
 configfs_group_operations

Le 15/12/2025 à 03:13, Baoquan He a écrit :
> On 12/14/25 at 06:57pm, Christophe JAILLET wrote:
>> 'struct configfs_item_operations' and 'configfs_group_operations' are not
>> modified in this driver.
>>
>> Constifying these structures moves some data to a read-only section, so
>> increases overall security, especially when the structure holds some
>> function pointers.
>>
>> On a x86_64, with allmodconfig, as an example:
>> Before:
>> ======
>>     text	   data	    bss	    dec	    hex	filename
>>    16339	  11001	    384	  27724	   6c4c	kernel/crash_dump_dm_crypt.o
>>
>> After:
>> =====
>>     text	   data	    bss	    dec	    hex	filename
>>    16499	  10841	    384	  27724	   6c4c	kernel/crash_dump_dm_crypt.o
>>
>> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> 
> Sounds not bad, leave this to Coiby to test.
> 
>> ---
>> Compile tested only.
>>
>> This change is possible since commits f2f36500a63b and f7f78098690d.
> 
> I don't follow here, why do these two commits have anything with this
> patch?

Without these patches, it won't compile because "struct 
config_item_type" needs to be tweaked to accept some const field. It is 
what is done by these patches that have landed 2 weeks ago or so.


Without these 2 commits, you would get (with French messages, sorry):

   CC      kernel/crash_dump_dm_crypt.o
kernel/crash_dump_dm_crypt.c:231:24: erreur: l'initialisation abandonne 
le qualificatif « const » du type pointé [-Werror=discarded-qualifiers]
   231 |         .ct_item_ops = &config_key_item_ops,
       |                        ^
kernel/crash_dump_dm_crypt.c:306:25: erreur: l'initialisation abandonne 
le qualificatif « const » du type pointé [-Werror=discarded-qualifiers]
   306 |         .ct_group_ops = &config_keys_group_ops,
       |                         ^

CJ

> 
>> ---
>>   kernel/crash_dump_dm_crypt.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/crash_dump_dm_crypt.c b/kernel/crash_dump_dm_crypt.c
>> index 401423ba477d..0d23dc1de67c 100644
>> --- a/kernel/crash_dump_dm_crypt.c
>> +++ b/kernel/crash_dump_dm_crypt.c
>> @@ -223,7 +223,7 @@ static void config_key_release(struct config_item *item)
>>   	key_count--;
>>   }
>>   
>> -static struct configfs_item_operations config_key_item_ops = {
>> +static const struct configfs_item_operations config_key_item_ops = {
>>   	.release = config_key_release,
>>   };
>>   
>> @@ -298,7 +298,7 @@ static struct configfs_attribute *config_keys_attrs[] = {
>>    * Note that, since no extra work is required on ->drop_item(),
>>    * no ->drop_item() is provided.
>>    */
>> -static struct configfs_group_operations config_keys_group_ops = {
>> +static const struct configfs_group_operations config_keys_group_ops = {
>>   	.make_item = config_keys_make_item,
>>   };
>>   
>> -- 
>> 2.52.0
>>
>>
> 
> 
>