CRED: Separate task security context from task_struct

Separate the task security context from task_struct.  At this point, the
security data is temporarily embedded in the task_struct with two pointers
pointing to it.

Note that the Alpha arch is altered as it refers to (E)UID and (E)GID in
entry.S via asm-offsets.

With comment fixes Signed-off-by: Marc Dionne <marc.c.dionne@gmail.com>

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 133 insertions, 22 deletions

diff --git a/include/linux/cred.h b/include/linux/cred.h
index b69222cc1fd2..3e65587a72e5 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -12,39 +12,150 @@
 #ifndef _LINUX_CRED_H
 #define _LINUX_CRED_H
 
-#define get_current_user()	(get_uid(current->user))
-
-#define task_uid(task)		((task)->uid)
-#define task_gid(task)		((task)->gid)
-#define task_euid(task)		((task)->euid)
-#define task_egid(task)		((task)->egid)
-
-#define current_uid()		(current->uid)
-#define current_gid()		(current->gid)
-#define current_euid()		(current->euid)
-#define current_egid()		(current->egid)
-#define current_suid()		(current->suid)
-#define current_sgid()		(current->sgid)
-#define current_fsuid()		(current->fsuid)
-#define current_fsgid()		(current->fsgid)
-#define current_cap()		(current->cap_effective)
+#include <linux/capability.h>
+#include <linux/key.h>
+#include <asm/atomic.h>
+
+struct user_struct;
+struct cred;
+
+/*
+ * COW Supplementary groups list
+ */
+#define NGROUPS_SMALL		32
+#define NGROUPS_PER_BLOCK	((unsigned int)(PAGE_SIZE / sizeof(gid_t)))
+
+struct group_info {
+	atomic_t	usage;
+	int		ngroups;
+	int		nblocks;
+	gid_t		small_block[NGROUPS_SMALL];
+	gid_t		*blocks[0];
+};
+
+/**
+ * get_group_info - Get a reference to a group info structure
+ * @group_info: The group info to reference
+ *
+ * This must be called with the owning task locked (via task_lock()) when task
+ * != current.  The reason being that the vast majority of callers are looking
+ * at current->group_info, which can not be changed except by the current task.
+ * Changing current->group_info requires the task lock, too.
+ */
+#define get_group_info(group_info)		\
+do {						\
+	atomic_inc(&(group_info)->usage);	\
+} while (0)
+
+/**
+ * put_group_info - Release a reference to a group info structure
+ * @group_info: The group info to release
+ */
+#define put_group_info(group_info)			\
+do {							\
+	if (atomic_dec_and_test(&(group_info)->usage))	\
+		groups_free(group_info);		\
+} while (0)
+
+extern struct group_info *groups_alloc(int);
+extern void groups_free(struct group_info *);
+extern int set_current_groups(struct group_info *);
+extern int set_groups(struct cred *, struct group_info *);
+extern int groups_search(struct group_info *, gid_t);
+
+/* access the groups "array" with this macro */
+#define GROUP_AT(gi, i) \
+	((gi)->blocks[(i) / NGROUPS_PER_BLOCK][(i) % NGROUPS_PER_BLOCK])
+
+extern int in_group_p(gid_t);
+extern int in_egroup_p(gid_t);
+
+/*
+ * The security context of a task
+ *
+ * The parts of the context break down into two categories:
+ *
+ *  (1) The objective context of a task.  These parts are used when some other
+ *	task is attempting to affect this one.
+ *
+ *  (2) The subjective context.  These details are used when the task is acting
+ *	upon another object, be that a file, a task, a key or whatever.
+ *
+ * Note that some members of this structure belong to both categories - the
+ * LSM security pointer for instance.
+ *
+ * A task has two security pointers.  task->real_cred points to the objective
+ * context that defines that task's actual details.  The objective part of this
+ * context is used whenever that task is acted upon.
+ *
+ * task->cred points to the subjective context that defines the details of how
+ * that task is going to act upon another object.  This may be overridden
+ * temporarily to point to another security context, but normally points to the
+ * same context as task->real_cred.
+ */
+struct cred {
+	atomic_t	usage;
+	uid_t		uid;		/* real UID of the task */
+	gid_t		gid;		/* real GID of the task */
+	uid_t		suid;		/* saved UID of the task */
+	gid_t		sgid;		/* saved GID of the task */
+	uid_t		euid;		/* effective UID of the task */
+	gid_t		egid;		/* effective GID of the task */
+	uid_t		fsuid;		/* UID for VFS ops */
+	gid_t		fsgid;		/* GID for VFS ops */
+	unsigned	securebits;	/* SUID-less security management */
+	kernel_cap_t	cap_inheritable; /* caps our children can inherit */
+	kernel_cap_t	cap_permitted;	/* caps we're permitted */
+	kernel_cap_t	cap_effective;	/* caps we can actually use */
+	kernel_cap_t	cap_bset;	/* capability bounding set */
+#ifdef CONFIG_KEYS
+	unsigned char	jit_keyring;	/* default keyring to attach requested
+					 * keys to */
+	struct key	*thread_keyring; /* keyring private to this thread */
+	struct key	*request_key_auth; /* assumed request_key authority */
+#endif
+#ifdef CONFIG_SECURITY
+	void		*security;	/* subjective LSM security */
+#endif
+	struct user_struct *user;	/* real user ID subscription */
+	struct group_info *group_info;	/* supplementary groups for euid/fsgid */
+	struct rcu_head	rcu;		/* RCU deletion hook */
+	spinlock_t	lock;		/* lock for pointer changes */
+};
+
+#define get_current_user()	(get_uid(current->cred->user))
+
+#define task_uid(task)		((task)->cred->uid)
+#define task_gid(task)		((task)->cred->gid)
+#define task_euid(task)		((task)->cred->euid)
+#define task_egid(task)		((task)->cred->egid)
+
+#define current_uid()		(current->cred->uid)
+#define current_gid()		(current->cred->gid)
+#define current_euid()		(current->cred->euid)
+#define current_egid()		(current->cred->egid)
+#define current_suid()		(current->cred->suid)
+#define current_sgid()		(current->cred->sgid)
+#define current_fsuid()		(current->cred->fsuid)
+#define current_fsgid()		(current->cred->fsgid)
+#define current_cap()		(current->cred->cap_effective)
 
 #define current_uid_gid(_uid, _gid)		\
 do {						\
-	*(_uid) = current->uid;			\
-	*(_gid) = current->gid;			\
+	*(_uid) = current->cred->uid;		\
+	*(_gid) = current->cred->gid;		\
 } while(0)
 
 #define current_euid_egid(_uid, _gid)		\
 do {						\
-	*(_uid) = current->euid;		\
-	*(_gid) = current->egid;		\
+	*(_uid) = current->cred->euid;		\
+	*(_gid) = current->cred->egid;		\
 } while(0)
 
 #define current_fsuid_fsgid(_uid, _gid)		\
 do {						\
-	*(_uid) = current->fsuid;		\
-	*(_gid) = current->fsgid;		\
+	*(_uid) = current->cred->fsuid;		\
+	*(_gid) = current->cred->fsgid;		\
 } while(0)
 
 #endif /* _LINUX_CRED_H */