Re: [PATCH] exporting capability code/name pairs (try #5.1)

Greg KH
2008-02-15T19:38:58Z

On Fri, Feb 15, 2008 at 12:38:02PM -0600, Serge E. Hallyn wrote:
> Quoting Kohei KaiGai (kaigai@ak.jp.nec.com):
> > Li Zefan wrote:
> > - snip -
> > >> +error1:
> > >> + kobject_put(capability_kobj);
> > >> +error0:
> > >> + printk(KERN_ERR "Unable to export capabilities\n");
> > >> +
> > >> + return 0;
> > >
> > > Should return -EFXXX ..
> >
> > Oops,
> > I fixed it as follows. Thanks for your pointed out.
> >
> > --------
> > This patch enables to export code/name of capabilities supported
> > on the running kernel.
> >
> > A newer kernel sometimes adds new capabilities, like CAP_MAC_ADMIN
> > at 2.6.25. However, we have no interface to disclose what capabilities
> > are supported on this kernel. Thus, we have to maintain libcap version
> > in appropriate one synchronously.
> >
> > This patch enables libcap to collect the list of capabilities on
> > run time, and provide them for users.
> > It helps to improve portability of library.
> >
> > It exports these information as regular files under /sys/kernel/capability.
> > The numeric node exports its name, the symbolic node exports its code.
> >
> > Please consider to put this patch on the queue of 2.6.25.
>
> Looks good, except don't you need to put the code in commoncap.c under a
> #ifdef SYSFS?
>
> thanks,
> -serge
>
> >
> > Thanks,
> > ===================================================
> > [kaigai@saba ~]$ ls -R /sys/kernel/capability/
> > /sys/kernel/capability/:
> > codes names version
> >
> > /sys/kernel/capability/codes:
> > 0 10 12 14 16 18 2 21 23 25 27 29 30 32 4 6 8
> > 1 11 13 15 17 19 20 22 24 26 28 3 31 33 5 7 9
> >
> > /sys/kernel/capability/names:
> > cap_audit_control cap_kill cap_net_raw cap_sys_nice
> > cap_audit_write cap_lease cap_setfcap cap_sys_pacct
> > cap_chown cap_linux_immutable cap_setgid cap_sys_ptrace
> > cap_dac_override cap_mac_admin cap_setpcap cap_sys_rawio
> > cap_dac_read_search cap_mac_override cap_setuid cap_sys_resource
> > cap_fowner cap_mknod cap_sys_admin cap_sys_time
> > cap_fsetid cap_net_admin cap_sys_boot cap_sys_tty_config
> > cap_ipc_lock cap_net_bind_service cap_sys_chroot
> > cap_ipc_owner cap_net_broadcast cap_sys_module
> > [kaigai@saba ~]$ cat /sys/kernel/capability/version
> > 0x20071026
> > [kaigai@saba ~]$ cat /sys/kernel/capability/codes/30
> > cap_audit_control
> > [kaigai@saba ~]$ cat /sys/kernel/capability/names/cap_sys_pacct
> > 20
> > [kaigai@saba ~]$
> > ===================================================

As you are adding new sysfs entries, please also add the needed
Documentation/ABI/ entries as well.

Also, this code can be cleaned up a lot by just using the basic kobject
attributes, and not rolling your own types here.

thanks,

greg k-h