Re: [Qemu-devel] [PATCH v2 1/1] block/gluster: improve defense over string to int conversion

[Markus Armbruster <armbru@redhat.com>]

Jeff Cody <jcody@redhat.com> writes:

> On Tue, Aug 09, 2016 at 02:20:09PM +0530, Prasanna Kumar Kalever wrote:
>> using atoi() for converting string to int may be error prone in case if
>> string supplied in the argument is not a fold of numerical number,
>> 
>> This is not a bug because in the existing code,
>> 
>> static QemuOptsList runtime_tcp_opts = {
>>     .name = "gluster_tcp",
>>     .head = QTAILQ_HEAD_INITIALIZER(runtime_tcp_opts.head),
>>     .desc = {
>>         ...
>>         {
>>             .name = GLUSTER_OPT_PORT,
>>             .type = QEMU_OPT_NUMBER,
>>             .help = "port number ...",
>>         },
>> ...
>> };
>> 
>> port type is QEMU_OPT_NUMBER, before we actually reaches atoi() port is already
>> defended by parse_option_number()
>> 
>> However It is a good practice to use function like parse_uint_full()
>> over atoi() to keep port self defended
>> 
>> Note: As now the port string to int conversion has its defence code set,
>> and also we understand that port argument is actually a string type,
>> in the follow up patch let's move port type from QEMU_OPT_NUMBER to
>> QEMU_OPT_STRING
>> 
>> Signed-off-by: Prasanna Kumar Kalever <prasanna.kalever@redhat.com>
>> ---
>> v1: Initial patch
>> v2: Address comments on v1 given by Markus
>> ---
>>  block/gluster.c | 11 ++++++++++-
>>  1 file changed, 10 insertions(+), 1 deletion(-)
>> 
>> diff --git a/block/gluster.c b/block/gluster.c
>> index 01b479f..edde1ad 100644
>> --- a/block/gluster.c
>> +++ b/block/gluster.c
>> @@ -14,6 +14,7 @@
>>  #include "qapi/qmp/qerror.h"
>>  #include "qemu/uri.h"
>>  #include "qemu/error-report.h"
>> +#include "qemu/cutils.h"
>>  
>>  #define GLUSTER_OPT_FILENAME        "filename"
>>  #define GLUSTER_OPT_VOLUME          "volume"
>> @@ -318,6 +319,7 @@ static struct glfs *qemu_gluster_glfs_init(BlockdevOptionsGluster *gconf,
>>      int ret;
>>      int old_errno;
>>      GlusterServerList *server;
>> +    unsigned long long port;
>>  
>>      glfs = glfs_new(gconf->volume);
>>      if (!glfs) {
>> @@ -330,10 +332,17 @@ static struct glfs *qemu_gluster_glfs_init(BlockdevOptionsGluster *gconf,
>>                                     GlusterTransport_lookup[server->value->type],
>>                                     server->value->u.q_unix.path, 0);
>>          } else {
>> +            if ((parse_uint_full(server->value->u.tcp.port, &port, 10) < 0) ||
>> +                (port > 65535)) {

Two pairs of superfluous parenthesis.  Better:

                if (parse_uint_full(server->value->u.tcp.port, &port, 10) < 0 ||
                    port > 65535) {

or, if you prefer to break before the operator (I do):

                if (parse_uint_full(server->value->u.tcp.port, &port, 10) < 0
                    || port > 65535) {

or, if you prefer to keep side effects out of complex conditionals:

                ret = parse_uint_full(server->value->u.tcp.port, &port, 10);
                if (ret < 0 || port > 65535) {

Maintainer's choice.  Perhaps Jeff can touch this up on commit.

>> +                error_setg(errp, "'%s' is not a valid port number",
>> +                           server->value->u.tcp.port);
>> +                errno = EINVAL;
>
> As long as we are range checking, we should probably kick back 0 as an
> invalid port number as well, right?

Port 0 is an oddity.  On the one hand, bind() interprets it as "pick an
ephemeral port for me".  That makes port 0 unusable with the classical
sockets interface.  On the other hand, IP doesn't treat port 0
specially.  You *can* send and receive port 0 packets with a raw socket
interface.

Anyway, I wouldn't bother rejecting port 0 here.  Just let the system do
its "pick an ephemeral port" magic.

>> +                goto out;
>> +            }
>>              ret = glfs_set_volfile_server(glfs,
>>                                     GlusterTransport_lookup[server->value->type],
>>                                     server->value->u.tcp.host,
>> -                                   atoi(server->value->u.tcp.port));
>> +                                   (int)port);
>>          }
>>  
>>          if (ret < 0) {
>> -- 
>> 2.7.4
>> 

Preferrably with the parenthesis cleaned up:
Reviewed-by: Markus Armbruster <armbru@redhat.com>