Messages in this thread | | | Date | Wed, 15 Nov 2006 21:08:55 +0900 | From | KaiGai Kohei <> | Subject | Re: [PATCH 1/1] security: introduce fs caps |
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Hi, Serge.
Serge E. Hallyn wrote: > Quoting Bill O'Donnell (billodo@sgi.com): >> 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 <kaigai@ak.jp.nec.com> - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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