Re: [PATCH v4] Added PR_SET_PROCTITLE_AREA option for prctl()

[KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>]

> >+		case PR_SET_PROCTITLE_AREA: {
> >+			struct mm_struct *mm = current->mm;
> >+			unsigned long addr = arg2;
> >+			unsigned long len = arg3;
> >+			unsigned long end = arg2 + arg3;
> >+
> >+			if (len > PAGE_SIZE)
> >+				return -EINVAL;
> >+
> >+			if (addr >= end)
> >+				return -EINVAL;
> >+
> >+			if (!access_ok(VERIFY_READ, addr, len))
> >+				return -EFAULT;
> >+
> >+			mutex_lock(&mm->arg_lock);
> >+			mm->arg_start = addr;
> 
> Is this safe? You're assigning a user-space pointer to kernel space...
> Don't we need copy_from_user()?

mm->arg_start, arg_end are defined so.
Please see current implementation. 


> >+			mm->arg_end = addr + len;
> 
> Since you already have 'end', no need to caculate this again. :)

Good catch :)