Re: 2.6.25 Kernel - Problems with capabilities

[David]

serge@xxxxxxxxxx wrote:
> Quoting David (david@xxxxxxxxxxxxxxx):
>   
> > serge@xxxxxxxxxx wrote:
> >     
> > > > /lib/libcap.so.1 -> libcap.so.1.92
> > > >
> > > > I guess that's 1.92 (should be the version shipped with SuSE 9.1).
> > > >     
> > > >         
> > > Ok, thanks, then it's definately not what I was thinking.
> > >
> > > (Will wait to check out your strace)
> > >   
> > >       
> > strace attached.
> >
> > Cheers
> > David
> >
> >     
>
> ...
>   
> > capget(0x20071026, 0, {, , })           = -1 EINVAL (Invalid argument)
> >     
>
> This is odd.  libcap-1.x should be passing in 0x19980330.
>
> Next, given the -EINVAL return value ntpd should be seeing a NULL result
> from cap_get_proc() and exiting right there.
>
> What version of ntpd is this?  (I must be looking at a wrong value, but
> even so the fact that cap_get_proc()->capget() is using 0x20071026 for
> version doesn't make sense)
>
>   
> > capset(0, 0, {CAP_NET_BIND_SERVICE|CAP_SYS_TIME, CAP_NET_BIND_SERVICE|CAP_SYS_TIME, CAP_NET_BIND_SERVICE|CAP_SYS_TIME}) = -1 EINVAL (Invalid argument)
> > time(NULL)                              = 1208803493
> > write(5, "21 Apr 19:44:53 ntpd[6118]: cap_"..., 92) = 92
> > munmap(0x40022000, 4096)                = 0
> > exit_group(-1)                          = ?
> > Process 6118 detached
> >     
>
>   
Oh dear .. more investigation... here's the source from libcap-1.92. 
capget() is being called with null arguments, which I guess returns with 
the latest version in ch.version ?

The switch then fails and the set gets called with version = 0 ??

Cheers
David

void _libcap_establish_api(void)
{
   struct __user_cap_header_struct ch;
   struct __user_cap_data_struct cs;

   if (_libcap_kernel_version) {
       _cap_debug("already identified kernal api 0x%.8x",
                  _libcap_kernel_version);
       return;
   }

   memset(&ch, 0, sizeof(ch));
   memset(&cs, 0, sizeof(cs));

   (void) capget(&ch, &cs);

   switch (ch.version) {

   case 0x19980330:
       _libcap_kernel_version = 0x19980330;
       _libcap_kernel_features = CAP_FEATURE_PROC;
       break;

   case 0x19990414:
       _libcap_kernel_version = 0x19990414;
       _libcap_kernel_features = CAP_FEATURE_PROC|CAP_FEATURE_FILE;
       break;

   default:
       _libcap_kernel_version = 0x00000000;
       _libcap_kernel_features = 0x00000000;
   }

   _cap_debug("version: %x, features: %x\n",
              _libcap_kernel_version, _libcap_kernel_features);
}


> thanks,
> -serge
>   

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