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SubjectRe: 2.6.25 Kernel - Problems with capabilities
serge@hallyn.com wrote:
> Quoting David (david@unsolicited.net):
>
>> serge@hallyn.com 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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