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SubjectRe: 2.6.25 Kernel - Problems with capabilities
Quoting David (david@unsolicited.net):
> 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);
> }

Interesting. The version I was looking at (1.10) has nothing like this.

I don't know what shipped with recent RedHat and Fedora distros, but I
guess based on this we can in fact expect more failures from at least
SuSe distros.

We can't reasonably have newer kernels reply to a query with an older
libcap version, so I don't know what to do here. Andrew, do you have
any ideas?

thanks,
-serge


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