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

[Jeff Cody]

On Wed, Aug 10, 2016 at 09:13:48AM +0200, Markus Armbruster wrote:
> Jeff Cody <address@hidden> 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 <address@hidden>
> >> ---
> >> 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 <address@hidden>

Thanks,

Applied to my block branch:

git://github.com/codyprime/qemu-kvm-jtc.git block

[Removed spurious parenthesis]

-Jeff