Re: [PATCH 2/4] mremap: don't do mm_populate(new_addr) on failure

[Oleg Nesterov]

On 06/30, David Rientjes wrote:
>
> On Sat, 20 Jun 2015, Oleg Nesterov wrote:
>
> > --- a/mm/mremap.c
> > +++ b/mm/mremap.c
> > @@ -574,8 +574,10 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned 
> > long, old_len,
> >             ret = move_vma(vma, addr, old_len, new_len, new_addr, &locked);
> >     }
> >  out:
> > -   if (ret & ~PAGE_MASK)
> > +   if (ret & ~PAGE_MASK) {
> >             vm_unacct_memory(charged);
> > +           locked = 0;
> > +   }
> >     up_write(&current->mm->mmap_sem);
> >     if (locked && new_len > old_len)
> >             mm_populate(new_addr + old_len, new_len - old_len);
>
> Perhaps I'm looking at the wrong tree (next-20150630), but why does
> setting locked to 0 here matter if it's unreferenced?

See the "if (locked && ...)" check before mm_populate(). We should
not do this if move_vma() fails.

Oleg.

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