Re: [PATCH 2/3] exporting capability name/code pairs (final#2)

From: Serge E. Hallyn
Date: Tue Feb 26 2008 - 15:58:47 EST

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Quoting Andrew G. Morgan (morgan@xxxxxxxxxx):
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
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> Acked-by: Andrew G. Morgan <morgan@xxxxxxxxxx>
> Tested-by: Andrew G. Morgan <morgan@xxxxxxxxxx>

Also

Acked-by: Serge Hallyn <serue@xxxxxxxxxx>
Tested-by: Serge Hallyn <serue@xxxxxxxxxx>

thanks,
-serge

(plus you taught me a thing or two about kernel makefiles...)

>
> Cheers
>
> Andrew
>
> Kohei KaiGai wrote:
> | [PATCH 2/3] exporting capability name/code pairs
> |
> | This patch enables to export code/name pairs of capabilities the running
> | kernel supported.
> |
> | 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 the running kernel. Thus, we have to maintain libcap
> | version in appropriate one synchronously.
> |
> | This patch enables libcap to collect the list of capabilities at 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.
> |
> | Signed-off-by: KaiGai Kohei <kaigai@xxxxxxxxxxxxx>
> | --
> | Documentation/ABI/testing/sysfs-kernel-capability | 23 +++++
> | scripts/mkcapnames.sh | 44 +++++++++
> | security/Makefile | 9 ++
> | security/commoncap.c | 99
> +++++++++++++++++++++
> | 4 files changed, 175 insertions(+), 0 deletions(-)
> |
> | diff --git a/Documentation/ABI/testing/sysfs-kernel-capability
> b/Documentation/ABI/testing/sysfs-kernel-capability
> | index e69de29..d4a14e7 100644
> | --- a/Documentation/ABI/testing/sysfs-kernel-capability
> | +++ b/Documentation/ABI/testing/sysfs-kernel-capability
> | @@ -0,0 +1,23 @@
> | +What: /sys/kernel/capability
> | +Date: Feb 2008
> | +Contact: KaiGai Kohei <kaigai@xxxxxxxxxxxxx>
> | +Description:
> | + The entries under /sys/kernel/capability are used to export
> | + the list of capabilities the running kernel supports.
> | +
> | + - /sys/kernel/capability/version
> | + returns the most preferable version number for the
> | + running kernel.
> | + e.g) $ cat /sys/kernel/capability/version
> | + 0x20071026
> | +
> | + - /sys/kernel/capability/code/<numerical representation>
> | + returns its symbolic representation, on reading.
> | + e.g) $ cat /sys/kernel/capability/codes/30
> | + cap_audit_control
> | +
> | + - /sys/kernel/capability/name/<symbolic representation>
> | + returns its numerical representation, on reading.
> | + e.g) $ cat /sys/kernel/capability/names/cap_sys_pacct
> | + 20
> | +
> | diff --git a/scripts/mkcapnames.sh b/scripts/mkcapnames.sh
> | index e69de29..5d36d52 100644
> | --- a/scripts/mkcapnames.sh
> | +++ b/scripts/mkcapnames.sh
> | @@ -0,0 +1,44 @@
> | +#!/bin/sh
> | +
> | +#
> | +# generate a cap_names.h file from include/linux/capability.h
> | +#
> | +
> | +CAPHEAD="`dirname $0`/../include/linux/capability.h"
> | +REGEXP='^#define CAP_[A-Z_]+[ ]+[0-9]+$'
> | +NUMCAP=`cat "$CAPHEAD" | egrep -c "$REGEXP"`
> | +
> | +echo '#ifndef CAP_NAMES_H'
> | +echo '#define CAP_NAMES_H'
> | +echo
> | +echo '/*'
> | +echo ' * Do NOT edit this file directly.'
> | +echo ' * This file is generated from include/linux/capability.h
> automatically'
> | +echo ' */'
> | +echo
> | +echo '#if !defined(SYSFS_CAP_NAME_ENTRY) ||
> !defined(SYSFS_CAP_CODE_ENTRY)'
> | +echo '#error cap_names.h should be included from security/capability.c'
> | +echo '#else'
> | +echo "#if $NUMCAP != CAP_LAST_CAP + 1"
> | +echo '#error mkcapnames.sh cannot collect capabilities correctly'
> | +echo '#else'
> | +cat "$CAPHEAD" | egrep "$REGEXP" \
> | + | awk '{ printf("SYSFS_CAP_NAME_ENTRY(%s,%s);\n", tolower($2),
> $2); }'
> | +echo
> | +echo 'static struct attribute *capability_name_attrs[] = {'
> | +cat "$CAPHEAD" | egrep "$REGEXP" \
> | + | awk '{ printf("\t&%s_name_attr.attr,\n", tolower($2)); } END {
> print "\tNULL," }'
> | +echo '};'
> | +
> | +echo
> | +cat "$CAPHEAD" | egrep "$REGEXP" \
> | + | awk '{ printf("SYSFS_CAP_CODE_ENTRY(%s,%s);\n", tolower($2),
> $2); }'
> | +echo
> | +echo 'static struct attribute *capability_code_attrs[] = {'
> | +cat "$CAPHEAD" | egrep "$REGEXP" \
> | + | awk '{ printf("\t&%s_code_attr.attr,\n", tolower($2)); } END {
> print "\tNULL," }'
> | +echo '};'
> | +
> | +echo '#endif'
> | +echo '#endif'
> | +echo '#endif'
> | diff --git a/security/Makefile b/security/Makefile
> | index 9e8b025..4093e3e 100644
> | --- a/security/Makefile
> | +++ b/security/Makefile
> | @@ -18,3 +18,12 @@ obj-$(CONFIG_SECURITY_SELINUX) += selinux/built-in.o
> | obj-$(CONFIG_SECURITY_SMACK) += commoncap.o smack/built-in.o
> | obj-$(CONFIG_SECURITY_CAPABILITIES) += commoncap.o capability.o
> | obj-$(CONFIG_SECURITY_ROOTPLUG) += commoncap.o root_plug.o
> | +
> | +# cap_names.h contains the code/name pair of capabilities.
> | +# It is generated using include/linux/capability.h automatically.
> | +$(obj)/commoncap.o: $(obj)/cap_names.h
> | +quiet_cmd_cap_names = CAPS $@
> | + cmd_cap_names = /bin/sh $(srctree)/scripts/mkcapnames.sh > $@
> | +targets += cap_names.h
> | +$(obj)/cap_names.h: $(srctree)/scripts/mkcapnames.sh
> $(srctree)/include/linux/capability.h FORCE
> | + $(call if_changed,cap_names)
> | diff --git a/security/commoncap.c b/security/commoncap.c
> | index 5aba826..9483fa9 100644
> | --- a/security/commoncap.c
> | +++ b/security/commoncap.c
> | @@ -24,6 +24,8 @@
> | #include <linux/hugetlb.h>
> | #include <linux/mount.h>
> | #include <linux/sched.h>
> | +#include <linux/kobject.h>
> | +#include <linux/sysfs.h>
> |
> | /* Global security state */
> |
> | @@ -637,3 +639,100 @@ int cap_vm_enough_memory(struct mm_struct *mm,
> long pages)
> | return __vm_enough_memory(mm, pages, cap_sys_admin);
> | }
> |
> | +/*
> | + * Export the list of capabilities on /sys/kernel/capability
> | + */
> | +static struct kobject *capability_kobj;
> | +
> | +static ssize_t capability_name_show(struct kobject *kobj,
> | + struct kobj_attribute *attr,
> | + char *buffer)
> | +{
> | + /* It returns numerical representation of capability. */
> | + return scnprintf(buffer, PAGE_SIZE, "%ld\n", (long) attr->data);
> | +}
> | +
> | +static ssize_t capability_code_show(struct kobject *kobj,
> | + struct kobj_attribute *attr,
> | + char *buffer)
> | +{
> | + /* It returns symbolic representation of capability. */
> | + return scnprintf(buffer, PAGE_SIZE, "%s\n", (char *) attr->data);
> | +}
> | +
> | +static ssize_t capability_version_show(struct kobject *kobj,
> | + struct kobj_attribute *attr,
> | + char *buffer)
> | +{
> | + return scnprintf(buffer, PAGE_SIZE, "0x%08x\n",
> | + _LINUX_CAPABILITY_VERSION);
> | +}
> | +
> | +#define SYSFS_CAP_NAME_ENTRY(_name,_code) \
> | + static struct kobj_attribute _name##_name_attr = \
> | + __ATTR_DATA(_name, 0444, capability_name_show, NULL, (long)(_code))
> | +
> | +#define SYSFS_CAP_CODE_ENTRY(_name,_code) \
> | + static struct kobj_attribute _name##_code_attr = \
> | + __ATTR_DATA(_code, 0444, capability_code_show, NULL,
> __stringify(_name))
> | +
> | +/*
> | + * capability_attrs[] is generated automatically by
> scripts/mkcapnames.sh
> | + * This script parses include/linux/capability.h
> | + */
> | +#include "cap_names.h"
> | +
> | +static struct attribute_group capability_name_attr_group = {
> | + .name = "names",
> | + .attrs = capability_name_attrs,
> | +};
> | +
> | +static struct attribute_group capability_code_attr_group = {
> | + .name = "codes",
> | + .attrs = capability_code_attrs,
> | +};
> | +
> | +static struct kobj_attribute cap_version_attr =
> | + __ATTR(version, 0444, capability_version_show, NULL);
> | +
> | +static int __init capability_export_names(void)
> | +{
> | + int rc = -ENOMEM;
> | +
> | + /* make /sys/kernel/capability */
> | + capability_kobj = kobject_create_and_add("capability", kernel_kobj);
> | + if (!capability_kobj)
> | + goto error0;
> | +
> | + /* make /sys/kernel/capability/names */
> | + rc = sysfs_create_group(capability_kobj,
> | + &capability_name_attr_group);
> | + if (rc)
> | + goto error1;
> | +
> | + /* make /sys/kernel/capability/codes */
> | + rc = sysfs_create_group(capability_kobj,
> | + &capability_code_attr_group);
> | + if (rc)
> | + goto error2;
> | +
> | + /* make /sys/kernel/capability/version */
> | + rc = sysfs_create_file(capability_kobj,
> | + &cap_version_attr.attr);
> | + if (rc)
> | + goto error3;
> | +
> | + return 0;
> | +
> | +error3:
> | + sysfs_remove_group(capability_kobj, &capability_code_attr_group);
> | +error2:
> | + sysfs_remove_group(capability_kobj, &capability_name_attr_group);
> | +error1:
> | + kobject_put(capability_kobj);
> | +error0:
> | + printk(KERN_ERR "Unable to export capabilities\n");
> | +
> | + return rc;
> | +}
> | +__initcall(capability_export_names);
> |
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Next message: Roland McGrath: "[PATCH] x86 tls prevent_tail_call"
Previous message: Geert Uytterhoeven: "Re: [2.6 patch] m68k: use KBUILD_DEFCONFIG"
In reply to: Andrew G. Morgan: "Re: [PATCH 2/3] exporting capability name/code pairs (final#2)"
Next in thread: Kohei KaiGai: "[PATCH 3/3] a new example to use kobject/kobj_attribute (final#2)"
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