Re: [PATCH v11 08/14] net, arm64: untag user pointers in tcp_zerocopy_receive

[Andrey Konovalov]

On Fri, Mar 15, 2019 at 9:03 PM Eric Dumazet <eric.dumazet@xxxxxxxxx> wrote:
>
>
>
> On 03/15/2019 12:51 PM, Andrey Konovalov wrote:
> > This patch is a part of a series that extends arm64 kernel ABI to allow to
> > pass tagged user pointers (with the top byte set to something else other
> > than 0x00) as syscall arguments.
> >
> > tcp_zerocopy_receive() uses provided user pointers for vma lookups, which
> > can only by done with untagged pointers.
> >
> > Untag user pointers in this function.
> >
> > Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
> > ---
> >  net/ipv4/tcp.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> > index 6baa6dc1b13b..89db3b4fc753 100644
> > --- a/net/ipv4/tcp.c
> > +++ b/net/ipv4/tcp.c
> > @@ -1758,6 +1758,8 @@ static int tcp_zerocopy_receive(struct sock *sk,
> >       int inq;
> >       int ret;
> >
> > +     address = untagged_addr(address);
> > +
> >       if (address & (PAGE_SIZE - 1) || address != zc->address)
>
> The second test will fail, if the top bits are changed in address but not in zc->address

Will fix in v12, thanks Eric!

>
> >               return -EINVAL;
> >
> >
>