Re: [PATCH v5] LSM: Multiple concurrent LSMs

[Casey Schaufler <casey@schaufler-ca.com>]

On 10/20/2012 8:06 PM, Tetsuo Handa wrote:
> Casey Schaufler wrote:
>> +#define call_int_hook(RC, FUNC, ...)					\
>> +	do {								\
>> +		int called = 0;						\
>> +		int thisrc;						\
>> +		int i;							\
>> +									\
>> +		RC = 0;							\
>> +		for (i = 1; i < lsm_count; i++) {			\
>> +			if (!composer_ops[i]->FUNC)			\
>> +				continue;				\
>> +			thisrc = composer_ops[i]->FUNC(__VA_ARGS__);	\
>> +			if (thisrc)					\
>> +				RC = thisrc;				\
>> +			called = 1;					\
>> +		}							\
>> +		if (!called && composer_ops[0]->FUNC)			\
>> +			RC = composer_ops[0]->FUNC(__VA_ARGS__);	\
>> +	} while (0)
> Why can't we simplify like below? What is special with composer_ops[0] ?

composer_ops[0] is the capability operations. They get called if and
only if no LSM supplies something for a particular hook. LSMs are allowed
to call the capability hook themselves or not as they see fit. Thus the
special case for composer_ops[0].

>
> #define call_int_hook(RC, FUNC, ...)					\
> 	do {								\
> 		int i;							\
> 									\
> 		RC = 0;							\
> 		for (i = 0; i < lsm_count; i++) {			\
> 			if (!composer_ops[i]->FUNC)			\
> 				continue;				\
> 			RC = composer_ops[i]->FUNC(__VA_ARGS__);	\
> 			if (RC)						\
> 				break;					\
> 		}							\
> 	} while (0)
>
>
>
>>  int security_inode_alloc(struct inode *inode)
>>  {
>> -	inode->i_security = NULL;
>> -	return security_ops->inode_alloc_security(inode);
>> +	int i;
>> +	int rc;
>> +	struct lsm_blob tblob;
>> +	struct lsm_blob *bp = NULL;
>> +
>> +	memset(&tblob, 0, sizeof(tblob));
>> +	inode->i_security = &tblob;
>> +
>> +	for (rc = 0, i = 1; i < lsm_count && rc == 0; i++)
>> +		if (composer_ops[i]->inode_alloc_security)
>> +			rc = composer_ops[i]->inode_alloc_security(inode);
>> +
>> +	if (tblob.lsm_setcount != 0) {
>> +		if (rc == 0)
>> +			bp = kmemdup(&tblob, sizeof(tblob), GFP_KERNEL);
>> +		if (bp == NULL) {
>> +			if (rc == 0)
>> +				rc = -ENOMEM;
>> +			for (i--; i >= 1; i--) {
>> +				if (composer_ops[i]->inode_free_security)
> 	if (!composer_ops[i]->inode_free_security)


Yes, indeed.


>
>> +					continue;
>> +				composer_ops[i]->inode_free_security(inode);
>> +			}
>> +			lsm_blob_cleanup(rc, &tblob, __func__);
>> +		}
>> +	}
>> +	inode->i_security = bp;
>> +	return rc;
>>  }
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