On 10/23/20 10:18 AM, Helge Deller wrote:
> On 10/23/20 9:25 AM, Rolf Eike Beer wrote:
>>> +#define O_NONBLOCK_OLD 000200004
>>> +#define O_NONBLOCK_MASK_OUT (O_NONBLOCK_OLD & ~O_NONBLOCK)
>>> +static int FIX_O_NONBLOCK(int flags)
>>> +{
>>> + if (flags & O_NONBLOCK_MASK_OUT) {
>>> + struct task_struct *tsk = current;
>>> + pr_warn("%s(%d) uses old O_NONBLOCK value. "
>>> + "Please recompile the application.\n",
>>> + tsk->comm, tsk->pid);
>>> + }
>>> + return flags & ~O_NONBLOCK_MASK_OUT;
>>> +}
>>
>> This will also trigger if I just pass 0x4 in flags, no? The check should be
>>
>> if ((flags & O_NONBLOCK_OLD) == O_NONBLOCK_OLD)
>
> RIGHT!
> That's a very good point.
> I was thinking about what would happen if over time a new (unrelated) define
> gets created which then gets 0x4 as value. My code would then have wrongly
> modified it.
After some more thinking....
It's not that easy.
Let's assume there will be another new flag at some time with value 0x4.
Now, the caller sets this flag (0x4) and new O_NONBLOCK (000200000),
so you end up with 000200004 again, which then triggers your check:
if ((flags & O_NONBLOCK_OLD) == O_NONBLOCK_OLD)
So, my check to test only the mask for 0x4 was basically better,
because it would prevent the usage of 0x4 as any new value.
In any way, it seems we need to avoid using 0x4 for a long time...
Helge
