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Add 64-bit capability support to the kernel
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The patch supports legacy (32-bit) capability userspace, and where possible
translates 32-bit capabilities to/from userspace and the VFS to 64-bit
kernel space capabilities.  If a capability set cannot be compressed into
32-bits for consumption by user space, the system call fails, with -ERANGE.

FWIW libcap-2.00 supports this change (and earlier capability formats)

 http://www.kernel.org/pub/linux/libs/security/linux-privs/kernel-2.6/

[akpm@linux-foundation.org: coding-syle fixes]
[akpm@linux-foundation.org: use get_task_comm()]
[ezk@cs.sunysb.edu: build fix]
[akpm@linux-foundation.org: do not initialise statics to 0 or NULL]
[akpm@linux-foundation.org: unused var]
[serue@us.ibm.com: export __cap_ symbols]
Signed-off-by: Andrew G. Morgan <morgan@kernel.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: James Morris <jmorris@namei.org>
Cc: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Andrew Morgan authored and Linus Torvalds committed Feb 5, 2008
1 parent 8f6936f commit e338d26
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Showing 7 changed files with 349 additions and 125 deletions.
10 changes: 5 additions & 5 deletions fs/nfsd/auth.c
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Original file line number Diff line number Diff line change
Expand Up @@ -11,8 +11,6 @@
#include <linux/nfsd/nfsd.h>
#include <linux/nfsd/export.h>

#define CAP_NFSD_MASK (CAP_FS_MASK|CAP_TO_MASK(CAP_SYS_RESOURCE))

int nfsexp_flags(struct svc_rqst *rqstp, struct svc_export *exp)
{
struct exp_flavor_info *f;
Expand Down Expand Up @@ -69,10 +67,12 @@ int nfsd_setuser(struct svc_rqst *rqstp, struct svc_export *exp)
ret = set_current_groups(cred.cr_group_info);
put_group_info(cred.cr_group_info);
if ((cred.cr_uid)) {
cap_t(current->cap_effective) &= ~CAP_NFSD_MASK;
current->cap_effective =
cap_drop_nfsd_set(current->cap_effective);
} else {
cap_t(current->cap_effective) |= (CAP_NFSD_MASK &
current->cap_permitted);
current->cap_effective =
cap_raise_nfsd_set(current->cap_effective,
current->cap_permitted);
}
return ret;
}
21 changes: 15 additions & 6 deletions fs/proc/array.c
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Original file line number Diff line number Diff line change
Expand Up @@ -281,14 +281,23 @@ static inline char *task_sig(struct task_struct *p, char *buffer)
return buffer;
}

static char *render_cap_t(const char *header, kernel_cap_t *a, char *buffer)
{
unsigned __capi;

buffer += sprintf(buffer, "%s", header);
CAP_FOR_EACH_U32(__capi) {
buffer += sprintf(buffer, "%08x",
a->cap[(_LINUX_CAPABILITY_U32S-1) - __capi]);
}
return buffer + sprintf(buffer, "\n");
}

static inline char *task_cap(struct task_struct *p, char *buffer)
{
return buffer + sprintf(buffer, "CapInh:\t%016x\n"
"CapPrm:\t%016x\n"
"CapEff:\t%016x\n",
cap_t(p->cap_inheritable),
cap_t(p->cap_permitted),
cap_t(p->cap_effective));
buffer = render_cap_t("CapInh:\t", &p->cap_inheritable, buffer);
buffer = render_cap_t("CapPrm:\t", &p->cap_permitted, buffer);
return render_cap_t("CapEff:\t", &p->cap_effective, buffer);
}

static inline char *task_context_switch_counts(struct task_struct *p,
Expand Down
221 changes: 155 additions & 66 deletions include/linux/capability.h
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Original file line number Diff line number Diff line change
Expand Up @@ -23,13 +23,20 @@ struct task_struct;
kernel might be somewhat backwards compatible, but don't bet on
it. */

/* XXX - Note, cap_t, is defined by POSIX to be an "opaque" pointer to
/* Note, cap_t, is defined by POSIX (draft) to be an "opaque" pointer to
a set of three capability sets. The transposition of 3*the
following structure to such a composite is better handled in a user
library since the draft standard requires the use of malloc/free
etc.. */

#define _LINUX_CAPABILITY_VERSION 0x19980330
#define _LINUX_CAPABILITY_VERSION_1 0x19980330
#define _LINUX_CAPABILITY_U32S_1 1

#define _LINUX_CAPABILITY_VERSION_2 0x20071026
#define _LINUX_CAPABILITY_U32S_2 2

#define _LINUX_CAPABILITY_VERSION _LINUX_CAPABILITY_VERSION_2
#define _LINUX_CAPABILITY_U32S _LINUX_CAPABILITY_U32S_2

typedef struct __user_cap_header_struct {
__u32 version;
Expand All @@ -42,43 +49,42 @@ typedef struct __user_cap_data_struct {
__u32 inheritable;
} __user *cap_user_data_t;


#define XATTR_CAPS_SUFFIX "capability"
#define XATTR_NAME_CAPS XATTR_SECURITY_PREFIX XATTR_CAPS_SUFFIX

#define XATTR_CAPS_SZ (3*sizeof(__le32))
#define VFS_CAP_REVISION_MASK 0xFF000000
#define VFS_CAP_FLAGS_MASK ~VFS_CAP_REVISION_MASK
#define VFS_CAP_FLAGS_EFFECTIVE 0x000001

#define VFS_CAP_REVISION_1 0x01000000
#define VFS_CAP_U32_1 1
#define XATTR_CAPS_SZ_1 (sizeof(__le32)*(1 + 2*VFS_CAP_U32_1))

#define VFS_CAP_REVISION VFS_CAP_REVISION_1
#define VFS_CAP_REVISION_2 0x02000000
#define VFS_CAP_U32_2 2
#define XATTR_CAPS_SZ_2 (sizeof(__le32)*(1 + 2*VFS_CAP_U32_2))

#define XATTR_CAPS_SZ XATTR_CAPS_SZ_2
#define VFS_CAP_U32 VFS_CAP_U32_2
#define VFS_CAP_REVISION VFS_CAP_REVISION_2

#define VFS_CAP_FLAGS_MASK ~VFS_CAP_REVISION_MASK
#define VFS_CAP_FLAGS_EFFECTIVE 0x000001

struct vfs_cap_data {
__u32 magic_etc; /* Little endian */
__le32 magic_etc; /* Little endian */
struct {
__u32 permitted; /* Little endian */
__u32 inheritable; /* Little endian */
} data[1];
__le32 permitted; /* Little endian */
__le32 inheritable; /* Little endian */
} data[VFS_CAP_U32];
};

#ifdef __KERNEL__

/* #define STRICT_CAP_T_TYPECHECKS */

#ifdef STRICT_CAP_T_TYPECHECKS

typedef struct kernel_cap_struct {
__u32 cap;
__u32 cap[_LINUX_CAPABILITY_U32S];
} kernel_cap_t;

#else

typedef __u32 kernel_cap_t;

#endif

#define _USER_CAP_HEADER_SIZE (2*sizeof(__u32))
#define _USER_CAP_HEADER_SIZE (sizeof(struct __user_cap_header_struct))
#define _KERNEL_CAP_T_SIZE (sizeof(kernel_cap_t))

#endif
Expand Down Expand Up @@ -121,10 +127,6 @@ typedef __u32 kernel_cap_t;

#define CAP_FSETID 4

/* Used to decide between falling back on the old suser() or fsuser(). */

#define CAP_FS_MASK 0x1f

/* Overrides the restriction that the real or effective user ID of a
process sending a signal must match the real or effective user ID
of the process receiving the signal. */
Expand All @@ -147,8 +149,12 @@ typedef __u32 kernel_cap_t;
** Linux-specific capabilities
**/

/* Transfer any capability in your permitted set to any pid,
remove any capability in your permitted set from any pid */
/* Without VFS support for capabilities:
* Transfer any capability in your permitted set to any pid,
* remove any capability in your permitted set from any pid
* With VFS support for capabilities (neither of above, but)
* Add any capability to the current process' inheritable set
*/

#define CAP_SETPCAP 8

Expand Down Expand Up @@ -309,70 +315,153 @@ typedef __u32 kernel_cap_t;

#define CAP_SETFCAP 31

/*
* Bit location of each capability (used by user-space library and kernel)
*/

#define CAP_TO_INDEX(x) ((x) >> 5) /* 1 << 5 == bits in __u32 */
#define CAP_TO_MASK(x) (1 << ((x) & 31)) /* mask for indexed __u32 */

#ifdef __KERNEL__

/*
* Internal kernel functions only
*/

#ifdef STRICT_CAP_T_TYPECHECKS
#define CAP_FOR_EACH_U32(__capi) \
for (__capi = 0; __capi < _LINUX_CAPABILITY_U32S; ++__capi)

# define CAP_FS_MASK_B0 (CAP_TO_MASK(CAP_CHOWN) \
| CAP_TO_MASK(CAP_DAC_OVERRIDE) \
| CAP_TO_MASK(CAP_DAC_READ_SEARCH) \
| CAP_TO_MASK(CAP_FOWNER) \
| CAP_TO_MASK(CAP_FSETID))

#if _LINUX_CAPABILITY_U32S != 2
# error Fix up hand-coded capability macro initializers
#else /* HAND-CODED capability initializers */

# define CAP_EMPTY_SET {{ 0, 0 }}
# define CAP_FULL_SET {{ ~0, ~0 }}
# define CAP_INIT_EFF_SET {{ ~CAP_TO_MASK(CAP_SETPCAP), ~0 }}
# define CAP_FS_SET {{ CAP_FS_MASK_B0, 0 }}
# define CAP_NFSD_SET {{ CAP_FS_MASK_B0|CAP_TO_MASK(CAP_SYS_RESOURCE), 0 }}

#endif /* _LINUX_CAPABILITY_U32S != 2 */

#define CAP_INIT_INH_SET CAP_EMPTY_SET

# define cap_clear(c) do { (c) = __cap_empty_set; } while (0)
# define cap_set_full(c) do { (c) = __cap_full_set; } while (0)
# define cap_set_init_eff(c) do { (c) = __cap_init_eff_set; } while (0)

#define cap_raise(c, flag) ((c).cap[CAP_TO_INDEX(flag)] |= CAP_TO_MASK(flag))
#define cap_lower(c, flag) ((c).cap[CAP_TO_INDEX(flag)] &= ~CAP_TO_MASK(flag))
#define cap_raised(c, flag) ((c).cap[CAP_TO_INDEX(flag)] & CAP_TO_MASK(flag))

#define CAP_BOP_ALL(c, a, b, OP) \
do { \
unsigned __capi; \
CAP_FOR_EACH_U32(__capi) { \
c.cap[__capi] = a.cap[__capi] OP b.cap[__capi]; \
} \
} while (0)

#define CAP_UOP_ALL(c, a, OP) \
do { \
unsigned __capi; \
CAP_FOR_EACH_U32(__capi) { \
c.cap[__capi] = OP a.cap[__capi]; \
} \
} while (0)

static inline kernel_cap_t cap_combine(const kernel_cap_t a,
const kernel_cap_t b)
{
kernel_cap_t dest;
CAP_BOP_ALL(dest, a, b, |);
return dest;
}

#define to_cap_t(x) { x }
#define cap_t(x) (x).cap
static inline kernel_cap_t cap_intersect(const kernel_cap_t a,
const kernel_cap_t b)
{
kernel_cap_t dest;
CAP_BOP_ALL(dest, a, b, &);
return dest;
}

#else
static inline kernel_cap_t cap_drop(const kernel_cap_t a,
const kernel_cap_t drop)
{
kernel_cap_t dest;
CAP_BOP_ALL(dest, a, drop, &~);
return dest;
}

#define to_cap_t(x) (x)
#define cap_t(x) (x)
static inline kernel_cap_t cap_invert(const kernel_cap_t c)
{
kernel_cap_t dest;
CAP_UOP_ALL(dest, c, ~);
return dest;
}

#endif
static inline int cap_isclear(const kernel_cap_t a)
{
unsigned __capi;
CAP_FOR_EACH_U32(__capi) {
if (a.cap[__capi] != 0)
return 0;
}
return 1;
}

#define CAP_EMPTY_SET to_cap_t(0)
#define CAP_FULL_SET to_cap_t(~0)
#define CAP_INIT_EFF_SET to_cap_t(~0 & ~CAP_TO_MASK(CAP_SETPCAP))
#define CAP_INIT_INH_SET to_cap_t(0)
static inline int cap_issubset(const kernel_cap_t a, const kernel_cap_t set)
{
kernel_cap_t dest;
dest = cap_drop(a, set);
return cap_isclear(dest);
}

#define CAP_TO_MASK(x) (1 << (x))
#define cap_raise(c, flag) (cap_t(c) |= CAP_TO_MASK(flag))
#define cap_lower(c, flag) (cap_t(c) &= ~CAP_TO_MASK(flag))
#define cap_raised(c, flag) (cap_t(c) & CAP_TO_MASK(flag))
/* Used to decide between falling back on the old suser() or fsuser(). */

static inline kernel_cap_t cap_combine(kernel_cap_t a, kernel_cap_t b)
static inline int cap_is_fs_cap(int cap)
{
kernel_cap_t dest;
cap_t(dest) = cap_t(a) | cap_t(b);
return dest;
const kernel_cap_t __cap_fs_set = CAP_FS_SET;
return !!(CAP_TO_MASK(cap) & __cap_fs_set.cap[CAP_TO_INDEX(cap)]);
}

static inline kernel_cap_t cap_intersect(kernel_cap_t a, kernel_cap_t b)
static inline kernel_cap_t cap_drop_fs_set(const kernel_cap_t a)
{
kernel_cap_t dest;
cap_t(dest) = cap_t(a) & cap_t(b);
return dest;
const kernel_cap_t __cap_fs_set = CAP_FS_SET;
return cap_drop(a, __cap_fs_set);
}

static inline kernel_cap_t cap_drop(kernel_cap_t a, kernel_cap_t drop)
static inline kernel_cap_t cap_raise_fs_set(const kernel_cap_t a,
const kernel_cap_t permitted)
{
kernel_cap_t dest;
cap_t(dest) = cap_t(a) & ~cap_t(drop);
return dest;
const kernel_cap_t __cap_fs_set = CAP_FS_SET;
return cap_combine(a,
cap_intersect(permitted, __cap_fs_set));
}

static inline kernel_cap_t cap_invert(kernel_cap_t c)
static inline kernel_cap_t cap_drop_nfsd_set(const kernel_cap_t a)
{
kernel_cap_t dest;
cap_t(dest) = ~cap_t(c);
return dest;
const kernel_cap_t __cap_fs_set = CAP_NFSD_SET;
return cap_drop(a, __cap_fs_set);
}

#define cap_isclear(c) (!cap_t(c))
#define cap_issubset(a,set) (!(cap_t(a) & ~cap_t(set)))

#define cap_clear(c) do { cap_t(c) = 0; } while(0)
#define cap_set_full(c) do { cap_t(c) = ~0; } while(0)
#define cap_mask(c,mask) do { cap_t(c) &= cap_t(mask); } while(0)
static inline kernel_cap_t cap_raise_nfsd_set(const kernel_cap_t a,
const kernel_cap_t permitted)
{
const kernel_cap_t __cap_nfsd_set = CAP_NFSD_SET;
return cap_combine(a,
cap_intersect(permitted, __cap_nfsd_set));
}

#define cap_is_fs_cap(c) (CAP_TO_MASK(c) & CAP_FS_MASK)
extern const kernel_cap_t __cap_empty_set;
extern const kernel_cap_t __cap_full_set;
extern const kernel_cap_t __cap_init_eff_set;

int capable(int cap);
int __capable(struct task_struct *t, int cap);
Expand Down
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