Re: [PATCH 5/5] Swap Migration V5: sys_migrate_pages interface

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On Tue, 1 Nov 2005, Andrew Morton wrote:

> Christoph Lameter <[email protected]> wrote:
>>
>> ...
>> Changes V3->V4:
>> - Add Ray's permissions check based on check_kill_permission().
>>
>> ...
>> +	/*
>> +	 * Permissions check like for signals.
>> +	 * See check_kill_permission()
>> +	 */
>> +	if ((current->euid ^ task->suid) && (current->euid ^ task->uid) &&
>> +	    (current->uid ^ task->suid) && (current->uid ^ task->uid) &&
>> +	    !capable(CAP_SYS_ADMIN)) {
>> +		err = -EPERM;
>> +		goto out;
>> +	}
>
> Obscure.  Can you please explain the thinking behind putting this check in
> here?  Preferably via a comment...

Also XOR is not a good substitute for a compare. Except in some
strange corner cases, the code will always take more CPU cycles
because XOR modifies oprands while compares don't need to.


Cheers,
Dick Johnson
Penguin : Linux version 2.6.13.4 on an i686 machine (5589.55 BogoMips).
Warning : 98.36% of all statistics are fiction.
.

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