Re: [PATCH v2] qemu-nbd: Fix a memleak in nbd_client_thread()

[Vladimir Sementsov-Ogievskiy]

03.12.2020 16:58, Alex Chen wrote:
> When the qio_channel_socket_connect_sync() fails
> we should goto 'out_socket' label to free the 'sioc' instead of
> goto 'out' label.
> In addition, there's a lot of redundant code in the successful branch
> and the error branch, optimize it.
>
> Reported-by: Euler Robot <euler.robot@huawei.com>
> Signed-off-by: Alex Chen <alex.chen@huawei.com>
> Signed-off-by: Eric Blake <eblake@redhat.com>
> ---
>   qemu-nbd.c | 38 +++++++++++++++-----------------------
>   1 file changed, 15 insertions(+), 23 deletions(-)
>
> diff --git a/qemu-nbd.c b/qemu-nbd.c
> index a7075c5419..9583ee1af6 100644
> --- a/qemu-nbd.c
> +++ b/qemu-nbd.c
> @@ -265,8 +265,8 @@ static void *nbd_client_thread(void *arg)
>       char *device = arg;
>       NBDExportInfo info = { .request_sizes = false, .name = g_strdup("") };
>       QIOChannelSocket *sioc;
> -    int fd;
> -    int ret;
> +    int fd = -1;
> +    int ret = EXIT_FAILURE;
>       pthread_t show_parts_thread;
>       Error *local_error = NULL;
>   
> @@ -278,26 +278,24 @@ static void *nbd_client_thread(void *arg)
>           goto out;
>       }
>   
> -    ret = nbd_receive_negotiate(NULL, QIO_CHANNEL(sioc),
> -                                NULL, NULL, NULL, &info, &local_error);
> -    if (ret < 0) {
> +    if (nbd_receive_negotiate(NULL, QIO_CHANNEL(sioc),
> +                              NULL, NULL, NULL, &info, &local_error) < 0) {
>           if (local_error) {
>               error_report_err(local_error);
>           }
> -        goto out_socket;
> +        goto out;
>       }
>   
>       fd = open(device, O_RDWR);
>       if (fd < 0) {
>           /* Linux-only, we can use %m in printf.  */
>           error_report("Failed to open %s: %m", device);
> -        goto out_socket;
> +        goto out;
>       }
>   
> -    ret = nbd_init(fd, sioc, &info, &local_error);
> -    if (ret < 0) {
> +    if (nbd_init(fd, sioc, &info, &local_error) < 0) {
>           error_report_err(local_error);
> -        goto out_fd;
> +        goto out;
>       }
>   
>       /* update partition table */
> @@ -311,24 +309,18 @@ static void *nbd_client_thread(void *arg)
>           dup2(STDOUT_FILENO, STDERR_FILENO);
>       }
>   
> -    ret = nbd_client(fd);
> -    if (ret) {
> -        goto out_fd;
> +    if (nbd_client(fd) == 0) {
> +        ret = EXIT_SUCCESS;

It's not obvious that nbd_client() returns 0 on success, it calls ioctl(), 
which may return something positive in theory..

So, with s/==/>=/, or with just

if (nbd_client(fd) < 0) {
  goto out;
}

ret = EXIT_SUCCESS;


(which is good common pattern I think)

:

Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

--
Best regards,
Vladimir