Re: [PATCH v2] net/9p/trans_virtio.c: add null terminal for mount tag

Dominique Martinet
2018-08-02T01:54:59Z

piaojun wrote on Thu, Aug 02, 2018:
> chan->tag is Non-null terminated which will result in printing messy code
> when debugging code. So we should add '\0' for tag to make the code more
> convenient and robust. In addition, I drop char->tag_len to simplify the
> code.

Some new lines in commit message would be appreciated.

That aside, I have a couple of nitpicks, but it looks good to me - thanks

>
> Signed-off-by: Jun Piao <piaojun@huawei.com>
> ---
> net/9p/trans_virtio.c | 15 +++++----------
> 1 file changed, 5 insertions(+), 10 deletions(-)
>
> diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
> index d422bfc..0fe9c37 100644
> --- a/net/9p/trans_virtio.c
> +++ b/net/9p/trans_virtio.c
> @@ -89,10 +89,8 @@ struct virtio_chan {
> unsigned long p9_max_pages;
> /* Scatterlist: can be too big for stack. */
> struct scatterlist sg[VIRTQUEUE_NUM];
> -
> - int tag_len;
> /*
> - * tag name to identify a mount Non-null terminated
> + * tag name to identify a mount null terminated
> */
> char *tag;
>
> @@ -529,10 +527,9 @@ static ssize_t p9_mount_tag_show(struct device *dev,
> vdev = dev_to_virtio(dev);
> chan = vdev->priv;
>
> - memcpy(buf, chan->tag, chan->tag_len);
> - buf[chan->tag_len] = 0;
> + memcpy(buf, chan->tag, strlen(chan->tag) + 1);
>
> - return chan->tag_len + 1;
> + return strlen(chan->tag) + 1;

Use a local variable for strlen(chan->tag)?

> }
>
> static DEVICE_ATTR(mount_tag, 0444, p9_mount_tag_show, NULL);
> @@ -585,7 +582,7 @@ 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;
> @@ -594,7 +591,6 @@ static int p9_virtio_probe(struct virtio_device *vdev)
> virtio_cread_bytes(vdev, offsetof(struct virtio_9p_config, tag),
> tag, tag_len);
> chan->tag = tag;
> - chan->tag_len = tag_len;
> err = sysfs_create_file(&(vdev->dev.kobj), &dev_attr_mount_tag.attr);
> if (err) {
> goto out_free_tag;
> @@ -654,8 +650,7 @@ static int p9_virtio_probe(struct virtio_device *vdev)
>
> mutex_lock(&virtio_9p_lock);
> list_for_each_entry(chan, &virtio_chan_list, chan_list) {
> - if (!strncmp(devname, chan->tag, chan->tag_len) &&
> - strlen(devname) == chan->tag_len) {
> + if (!strncmp(devname, chan->tag, strlen(chan->tag) + 1)) {

strncmp(x, y, strlen(y)+1) is precisely what strcmp does so let's use
the simpler version

--
Dominique