[RFC] [PATCH 2/2] capabilities: implement 64-bit capabilities

["Serge E. Hallyn" <serue@us.ibm.com>]

>From 7dd503c612afcb86b3165602ab264e2e9493b4bf Mon Sep 17 00:00:00 2001
From: Serge E. Hallyn <serue@us.ibm.com>
Date: Mon, 15 Oct 2007 20:57:52 -0400
Subject: [RFC] [PATCH 2/2] capabilities: implement 64-bit capabilities

We are out of capabilities in the 32-bit capability fields, and
several users could make use of additional capabilities.
Convert the capabilities to 64-bits, change the capability
version number accordingly, and convert the file capability
code to handle both 32-bit and 64-bit file capability xattrs.

It might seem desirable to also implement back-compatibility
to read 32-bit caps from userspace, but that becomes
problematic with capget, as capget could return valid info
for processes not using high bits, but would have to return
-EINVAL for those which were.

So with this patch, libcap would need to be updated to make
use of capset/capget.

Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
---
 fs/proc/array.c            |    6 +++---
 include/linux/capability.h |   29 ++++++++++++++++++++---------
 security/commoncap.c       |   37 +++++++++++++++++++++++++++++--------
 3 files changed, 52 insertions(+), 20 deletions(-)

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 3f4d824..c8ea46d 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -288,9 +288,9 @@ static inline char *task_sig(struct task_struct *p, char *buffer)
 
 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",
+    return buffer + sprintf(buffer, "CapInh:\t%016lx\n"
+			    "CapPrm:\t%016lx\n"
+			    "CapEff:\t%016lx\n",
 			    cap_t(p->cap_inheritable),
 			    cap_t(p->cap_permitted),
 			    cap_t(p->cap_effective));
diff --git a/include/linux/capability.h b/include/linux/capability.h
index bb017ed..a3da4b9 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -29,7 +29,7 @@ struct task_struct;
    library since the draft standard requires the use of malloc/free
    etc.. */
 
-#define _LINUX_CAPABILITY_VERSION  0x19980330
+#define _LINUX_CAPABILITY_VERSION  0x20071015
 
 typedef struct __user_cap_header_struct {
 	__u32 version;
@@ -37,29 +37,40 @@ typedef struct __user_cap_header_struct {
 } __user *cap_user_header_t;
 
 typedef struct __user_cap_data_struct {
-        __u32 effective;
-        __u32 permitted;
-        __u32 inheritable;
+        __u64 effective;
+        __u64 permitted;
+        __u64 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 XATTR_CAPS_SZ_1 (3*sizeof(__le32))
+#define XATTR_CAPS_SZ_2 (2*sizeof(__le64) + sizeof(__le32))
 #define VFS_CAP_REVISION_MASK	0xFF000000
 #define VFS_CAP_REVISION_1	0x01000000
+#define VFS_CAP_REVISION_2	0x02000000
 
-#define VFS_CAP_REVISION	VFS_CAP_REVISION_1
+#define VFS_CAP_REVISION	VFS_CAP_REVISION_2
+#define XATTR_CAPS_SZ		XATTR_CAPS_SZ_2
 
 #define VFS_CAP_FLAGS_MASK	~VFS_CAP_REVISION_MASK
 #define VFS_CAP_FLAGS_EFFECTIVE	0x000001
 
-struct vfs_cap_data {
+struct vfs_cap_data_v1 {
 	__u32 magic_etc;  /* Little endian */
 	__u32 permitted;    /* Little endian */
 	__u32 inheritable;  /* Little endian */
 };
 
+struct vfs_cap_data_v2 {
+	__u32 magic_etc;  /* Little endian */
+	__u64 permitted;    /* Little endian */
+	__u64 inheritable;  /* Little endian */
+};
+
+typedef struct vfs_cap_data_v2 vfs_cap_data;
+
 #ifdef __KERNEL__
 
 /* #define STRICT_CAP_T_TYPECHECKS */
@@ -67,12 +78,12 @@ struct vfs_cap_data {
 #ifdef STRICT_CAP_T_TYPECHECKS
 
 typedef struct kernel_cap_struct {
-	__u32 cap;
+	__u64 cap;
 } kernel_cap_t;
 
 #else
 
-typedef __u32 kernel_cap_t;
+typedef __u64 kernel_cap_t;
 
 #endif
 
diff --git a/security/commoncap.c b/security/commoncap.c
index 542bbe9..2cca843 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -190,25 +190,46 @@ int cap_inode_killpriv(struct dentry *dentry)
 	return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS);
 }
 
-static inline int cap_from_disk(struct vfs_cap_data *caps,
+union vfs_cap_union {
+	struct vfs_cap_data_v1 v1;
+	struct vfs_cap_data_v2 v2;
+};
+
+static inline int cap_from_disk(union vfs_cap_union *caps,
 				struct linux_binprm *bprm,
 				int size)
 {
 	__u32 magic_etc;
 
-	if (size != XATTR_CAPS_SZ)
+	if (size != XATTR_CAPS_SZ_1 && size != XATTR_CAPS_SZ_2)
 		return -EINVAL;
 
-	magic_etc = le32_to_cpu(caps->magic_etc);
+	magic_etc = le32_to_cpu(caps->v1.magic_etc);
 
 	switch ((magic_etc & VFS_CAP_REVISION_MASK)) {
-	case VFS_CAP_REVISION:
+	case VFS_CAP_REVISION_1:
+		if (size != XATTR_CAPS_SZ_1)
+			return -EINVAL;
+		if (magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
+			bprm->cap_effective = true;
+		else
+			bprm->cap_effective = false;
+		bprm->cap_permitted = to_cap_t(
+			(__u64) le32_to_cpu(caps->v1.permitted) );
+		bprm->cap_inheritable = to_cap_t(
+			(__u64) le32_to_cpu(caps->v1.inheritable) );
+		return 0;
+	case VFS_CAP_REVISION_2:
+		if (size != XATTR_CAPS_SZ_2)
+			return -EINVAL;
 		if (magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
 			bprm->cap_effective = true;
 		else
 			bprm->cap_effective = false;
-		bprm->cap_permitted = to_cap_t( le32_to_cpu(caps->permitted) );
-		bprm->cap_inheritable = to_cap_t( le32_to_cpu(caps->inheritable) );
+		bprm->cap_permitted = to_cap_t(
+			le64_to_cpu(caps->v2.permitted) );
+		bprm->cap_inheritable = to_cap_t(
+			le64_to_cpu(caps->v2.inheritable) );
 		return 0;
 	default:
 		return -EINVAL;
@@ -220,7 +241,7 @@ static int get_file_caps(struct linux_binprm *bprm)
 {
 	struct dentry *dentry;
 	int rc = 0;
-	struct vfs_cap_data incaps;
+	union vfs_cap_union incaps;
 	struct inode *inode;
 
 	if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID) {
@@ -235,7 +256,7 @@ static int get_file_caps(struct linux_binprm *bprm)
 
 	rc = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0);
 	if (rc > 0) {
-		if (rc == XATTR_CAPS_SZ)
+		if (rc == XATTR_CAPS_SZ_2 || rc == XATTR_CAPS_SZ_1)
 			rc = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS,
 						&incaps, XATTR_CAPS_SZ);
 		else
-- 
1.5.1.1.GIT