Re: [PATCH v3 2/3] lsm: introduce security_lsm_config_*_policy hooks

["Maxime Bélair" <maxime.belair@canonical.com>]

On 6/25/25 03:08, Tetsuo Handa wrote:
> On 2025/06/24 23:30, Maxime Bélair wrote:
>> +config LSM_CONFIG_SELF_POLICY_MAX_BUFFER_SIZE
>> +	int "Maximum buffer size for lsm_config_self_policy"
>> +	range 16384 1073741824
>> +	depends on SECURITY
>> +	default 4194304
>> +	help
>> +	  The maximum size of the buffer argument of lsm_config_self_policy.
>> +
>> +	  The default value of 4194304 (4MiB) is reasonable and should be large
>> +	  enough to fit policies in for most cases.
>> +
> 
> Do we want to define LSM_CONFIG_{SELF,SYSTEM}_POLICY_MAX_BUFFER_SIZE as Kconfig?
> 
> If security_lsm_config_{self,system}_policy() are meant to be used by multiple
> LSM modules, the upper limit each LSM module wants to impose would vary. Also,
> 1073741824 is larger than KMALLOC_MAX_SIZE; kmalloc()-based memory copying
> functions will hit WARN_ON_ONCE_GFP() at __alloc_frozen_pages_noprof().
> 
> Since some of LSM modules might use vmalloc()-based memory copying functions from
> security_lsm_config_{self,system}_policy(), the upper limit should be imposed by
> individual LSM module which provides security_lsm_config_{self,system}_policy().
> 
That makes sense. I removed this global Kconfig and the maximum buffer
size is now defined per module.