On Fri, 2022-06-10 at 21:06 +0300, Kirill A. Shutemov wrote: > On Fri, Jun 10, 2022 at 04:16:01PM +0000, Edgecombe, Rick P wrote: > > On Fri, 2022-06-10 at 17:35 +0300, Kirill A. Shutemov wrote: > > > +static int prctl_enable_tagged_addr(unsigned long nr_bits) > > > +{ > > > + struct mm_struct *mm = current->mm; > > > + > > > + /* Already enabled? */ > > > + if (mm->context.lam_cr3_mask) > > > + return -EBUSY; > > > + > > > + /* LAM has to be enabled before spawning threads */ > > > + if (get_nr_threads(current) > 1) > > > + return -EBUSY; > > > > Does this work for vfork()? I guess the idea is that locking is not > > needed below because there is only one thread with the MM, but with > > vfork() another task could operate on the MM, call fork(), etc. I'm > > not > > sure... > > I'm not sure I follow. vfork() blocks parent process until child exit > or > execve(). I don't see how it is a problem. Oh yea, you're right.