Hi, Serge.
Serge E. Hallyn wrote:
Quoting Bill O'Donnell ([email protected]):
8102 execve("/sbin/setfcaps", ["setfcaps", "cap_net_raw=ep", "/bin/ping"], [/* 67 vars */]) = 0
- snip -
8102 capget(0x19980330, 0, {0, 0, 0}) = -1 EINVAL (Invalid argument)
I don't see why this capget is returning -EINVAL. In fact I don't see
why it happens at all - cap_inode_setxattr would check
capable(CAP_SYS_ADMIN), but setxattr hasn't been called yet. Looking at
both libcap and setfcaps.c, I don't see where the capget comes from.
As for the -EINVAL, kernel/capability.c:sys_capget() returns -EINVAL if
the _LINUX_CAPABILITY_VERSION is wrong - you have 0x19980330 which is
correct - if pid < 0 - but you send in 0 - or if security_capget
returns -EINVAL, which cap_capget (and dummy_capget) don't do.
Kaigai, do you have any ideas?
Bill said that he uses SLES10/ia64, so the version of libcap is different
from Fedora Core's one. 'libcap-1.92-499.4.src.rpm' is bandled.
Then, I found a strange code in libcap-1.92-499.4.src.rpm.
The setfcaps calls cap_from_text() which is defined in libcap to parse
the command line argument. It has the following function call chains:
cap_from_text()
-> cap_init()
-> _libcap_establish_api()
---- the definition of _libcap_establish_api() ----
void _libcap_establish_api(void)
{
struct __user_cap_header_struct ch;
struct __user_cap_data_struct cs;
if (_libcap_kernel_version) { <-- _libcap_kernel_version is 0 initially.
_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);
}
---------------------------------------------------
capget() is called from _libcap_establish_api() with full-zeroed
__user_cap_header_struct object at first time.
The result of this, sys_capget() in kernel will return -EINVAL.
(Why did strace say the first argument is 0x19980330?)
Probably, Bill didn't update libcap.so.
But I can't recommend Bill to update libcap immediately.
As Hawk Xu said, it may cause a serious problem on the distro
except Fedora Core 6. :(
I have to recommend to use 'fscaps-1.0-kg.i386.rpm' now.
It includes the implementation of interaction between application and xattr.
(Of couse, it's one of the features which should be provided by libcap.)
Thanks,
--
Open Source Software Promotion Center, NEC
KaiGai Kohei <[email protected]>
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