On Wed, 1 Aug 2018 16:24:27 +0800
piaojun <piao...@huawei.com> wrote:
> Hi Dominique,
>
> On 2018/8/1 16:11, Dominique Martinet wrote:
> > piaojun wrote on Wed, Aug 01, 2018:
> >> chan->tag has no terminal char at last which will result in printing messy
> >> code when debugging code. So we should add '\0' for tag.
> >
> > 9p is full of non null-terminated string so I'm not sure how I feel
> > about it, is there anything wrong with how this is used or was this just
> > when you tried to printf it?
>
The mount tag isn't a 9P thingy actually. It is provided by the server
in the device config space, and it is never used in any 9P message.
It could have been a nul terminated string from the beginning. Not
sure why people opted to store it that way.
> There is nothing wrong at the places using tag, as they calculated the
> tag_len carefully. Adding '\0' for it will make the code more robust. And
> I'm glad to hear others' opinions.
>
So this patch basically turns chan->tag into a nul terminated string,
which is indeed more convenient and robust. Maybe you can update the
rest of the code accordingly and drop chan->tag_len then ?
> Thanks,
> Jun
>
> >
> > If it's just for debugging I'd suggest using the printf format "%.*s"
> > with "chan->tag_len, chan->tag" arguments,
FWIW, 9P strings received from the client are also converted to
nul terminated strings:
static int
p9pdu_vreadf(struct p9_fcall *pdu, int proto_version, const char *fmt,
va_list ap)
{
[...]
case 's':{
[...]
*sptr = kmalloc(len + 1, GFP_NOFS);
[...]
(*sptr)[len] = 0;
}
Cheers,
--
Greg
> >
> >
> > That said it's not like this is costly, so I'll take it if someone else
> > thinks this is helpful
> >
> >>
> >> Signed-off-by: Jun Piao <piao...@huawei.com>
> >> ---
> >> net/9p/trans_virtio.c | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
> >> index d422bfc..49d71d6 100644
> >> --- a/net/9p/trans_virtio.c
> >> +++ b/net/9p/trans_virtio.c
> >> @@ -585,7 +585,7 @@ static int p9_virtio_probe(struct virtio_device *vdev)
> >> err = -EINVAL;
> >> goto out_free_vq;
> >> }
> >> - tag = kmalloc(tag_len, GFP_KERNEL);
> >> + tag = kzalloc(tag_len + 1, GFP_KERNEL);
> >> if (!tag) {
> >> err = -ENOMEM;
> >> goto out_free_vq;
> >> --
