Re: [Qemu-devel] [PATCH for-2.9] sockets: Fix socket_address_to_string() hostname truncation

[Paolo Bonzini <pbonzini@redhat.com>]

On 23/03/2017 12:23, Markus Armbruster wrote:
> We first snprintf() to a fixed buffer, then g_strdup() the result
> *boggle*.
> 
> Worse, the size of the fixed buffer INET6_ADDRSTRLEN + 5 + 4 is bogus:
> the 4 correctly accounts for '[', ']', ':' and '\0', but
> INET6_ADDRSTRLEN is not a suitable limit for inet->host, and 5 is not
> one for inet->port!  They are for host and port in *numeric* form
> (exploiting that INET6_ADDRSTRLEN > INET_ADDRSTRLEN), but inet->host
> can also be a hostname, and inet->port can be a service name, to be
> resolved with getaddrinfo().
> 
> Fortunately, the only user so far is the "socket" network backend's
> net_socket_connected(), which uses it to initialize a NetSocketState's
> info_str[].  info_str[] has considerable more space: 256 instead of
> 55.  So the bug's impact appears to be limited to truncated "info
> networks" with the "socket" network backend.
> 
> The fix is obvious: use g_strdup_printf().
> 
> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> ---
>  util/qemu-sockets.c | 9 ++-------
>  1 file changed, 2 insertions(+), 7 deletions(-)
> 
> diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c
> index 7c120c4..40164bf 100644
> --- a/util/qemu-sockets.c
> +++ b/util/qemu-sockets.c
> @@ -1307,19 +1307,14 @@ char *socket_address_to_string(struct SocketAddress *addr, Error **errp)
>  {
>      char *buf;
>      InetSocketAddress *inet;
> -    char host_port[INET6_ADDRSTRLEN + 5 + 4];

/me learnt about INET6_ADDRSTRLEN today.

>      switch (addr->type) {
>      case SOCKET_ADDRESS_KIND_INET:
>          inet = addr->u.inet.data;
>          if (strchr(inet->host, ':') == NULL) {
> -            snprintf(host_port, sizeof(host_port), "%s:%s", inet->host,
> -                    inet->port);
> -            buf = g_strdup(host_port);
> +            buf = g_strdup_printf("%s:%s", inet->host, inet->port);
>          } else {
> -            snprintf(host_port, sizeof(host_port), "[%s]:%s", inet->host,
> -                    inet->port);
> -            buf = g_strdup(host_port);
> +            buf = g_strdup_printf("[%s]:%s", inet->host, inet->port);
>          }
>          break;
>  
> 

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>