Re: [RFC PATCH v9 3/4] drm/virtio: implement userptr resource support

[Dmitry Osipenko <dmitry.osipenko@collabora.com>]

09.10.2026 21:38, Dmitry Osipenko пишет:
> 24.09.2026 12:55, Honglei Huang пишет:
>> +	mm = current->mm;
>> +	mmgrab(mm);
>> +	lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
>> +	new_pinned = atomic64_add_return(userptr->npages, &mm->pinned_vm);
>> +	if (new_pinned < 0 ||
>> +	    (new_pinned > lock_limit && !capable(CAP_IPC_LOCK))) {
>> +		atomic64_sub(userptr->npages, &mm->pinned_vm)
> 
> At a quick glance over other kernel code touching pinned_vm, nobody else
> check for new_pinned < 0 and then doing atomic64_sub() for the negative
> value will be incorrect.
Though no, negative will restore pinned_vm. Still neg looks confusing
and shouldn't be needed as such overflow shouldn't be possible.

-- 
Best regards,
Dmitry