On Mon, Mar 14, 2016 at 7:41 PM, Eric Blake <ebl...@redhat.com> wrote:
> On 03/12/2016 01:39 AM, Pooja Dhannawat wrote:
> > Signed-off-by: Pooja Dhannawat <dhannawatpoo...@gmail.com>
> > ---
> > net/net.c | 8 ++++++--
> > 1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/net/net.c b/net/net.c
> > index b0c832e..5399758 100644
> > --- a/net/net.c
> > +++ b/net/net.c
> > @@ -709,16 +709,18 @@ ssize_t qemu_send_packet_raw(NetClientState *nc,
> const uint8_t *buf, int size)
> > static ssize_t nc_sendv_compat(NetClientState *nc, const struct iovec
> *iov,
> > int iovcnt, unsigned flags)
> > {
> > - uint8_t buf[NET_BUFSIZE];
> > + uint8_t *buf;
> > uint8_t *buffer;
> > size_t offset;
> >
> > + buf = g_new(uint8_t, 1);
>
> If you're only going to malloc() one byte, it's more efficient to just
> stack-allocate it:
>
> uint8_t buf[1];
>
> Did you mean to do:
>
> buf = g_new(uint8_t, NET_BUFSIZE)
>
> instead?
>
> Yes, my bad, I meant NET_BUFSIZE.
> > +
> > if (iovcnt == 1) {
> > buffer = iov[0].iov_base;
> > offset = iov[0].iov_len;
> > } else {
> > buffer = buf;
> > - offset = iov_to_buf(iov, iovcnt, 0, buf, sizeof(buf));
> > + offset = iov_to_buf(iov, iovcnt, 0, (uint8_t *)buf,
> sizeof(uint8_t));
>
> This is wrong. The old code used NET_BUFSIZE bytes for iov_to_buf(),
> the new code uses only one byte. By the way, sizeof(char) and
> sizeof(uint8_t) are pointless in code, as they are strictly equivalent to
> 1.
>
> I agree that the idea behind the patch is useful (NET_BUFSIZE is 68k,
> which is too large for our goal of at most 4k stack allocation if we
> never want to overflow a stack guard page), but you'll need a correct
> working version of the patch.
>
> Yes, I will correct it and send next version of patch.
> --
> Eric Blake eblake redhat com +1-919-301-3266
> Libvirt virtualization library http://libvirt.org
>
>
