On Mon, 15 Apr 2013, Michel Lespinasse wrote:
> On Mon, Apr 15, 2013 at 2:47 PM, Hugh Dickins <hu...@google.com> wrote:
> > --- 3.9-rc7/mm/mlock.c 2013-04-01 09:08:05.736012852 -0700
> > +++ linux/mm/mlock.c 2013-04-15 14:20:24.454773245 -0700
> > @@ -397,8 +397,7 @@ int __mm_populate(unsigned long start, u
> > long ret = 0;
> >
> > VM_BUG_ON(start & ~PAGE_MASK);
> > - VM_BUG_ON(len != PAGE_ALIGN(len));
> > - end = start + len;
> > + end = start + PAGE_ALIGN(len);
> >
> > for (nstart = start; nstart < end; nstart = nend) {
> > /*
>
> Yes, there was originally an issue with page alignment in mmap as well, which
> was fixed by making sure mmap now passes the page aligned length to
> mm_populate().
>
> sys_brk() passes the length as the difference of two page aligned addresses,
> so it's fine. But vm_brk() doesn't - it calls do_brk() which page aligns the
> length, but then vm_brk passes the unaligned length to mm_populate().
>
> What do you think of the following ? len is already a PAGE_SIZE multiple when
> called from sys_brk()...
Yes, that's good.
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 0db0de1c2fbe..6af8b0d1c7db 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -2557,10 +2557,6 @@ static unsigned long do_brk(unsigned long addr,
> unsigned long len)
> pgoff_t pgoff = addr >> PAGE_SHIFT;
> int error;
>
> - len = PAGE_ALIGN(len);
> - if (!len)
> - return addr;
> -
> flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
>
> error = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
> @@ -2643,6 +2639,10 @@ unsigned long vm_brk(unsigned long addr, unsigned long
> len)
> unsigned long ret;
> bool populate;
>
> + len = PAGE_ALIGN(len);
> + if (!len)
> + return addr;
> +
> down_write(&mm->mmap_sem);
> ret = do_brk(addr, len);
> populate = ((mm->def_flags & VM_LOCKED) != 0);
>
> --
> Michel "Walken" Lespinasse
> A program is never fully debugged until the last user dies.
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