1 files changed, 319 insertions, 23 deletions

diff --git a/include/linux/cred.h b/include/linux/cred.h
index b69222cc1fd2..3282ee4318e7 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -1,4 +1,4 @@
-/* Credentials management
+/* Credentials management - see Documentation/credentials.txt
  *
  * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
@@ -12,39 +12,335 @@
 #ifndef _LINUX_CRED_H
 #define _LINUX_CRED_H
 
-#define get_current_user()	(get_uid(current->user))
+#include <linux/capability.h>
+#include <linux/key.h>
+#include <asm/atomic.h>
 
-#define task_uid(task)		((task)->uid)
-#define task_gid(task)		((task)->gid)
-#define task_euid(task)		((task)->euid)
-#define task_egid(task)		((task)->egid)
+struct user_struct;
+struct cred;
+struct inode;
 
-#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)
+/*
+ * 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 gets a reference to a set of supplementary groups.
+ *
+ * If the caller is accessing a task's credentials, they must hold the RCU read
+ * lock when reading.
+ */
+static inline struct group_info *get_group_info(struct group_info *gi)
+{
+	atomic_inc(&gi->usage);
+	return gi;
+}
+
+/**
+ * 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 struct group_info init_groups;
+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(const 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 common credentials for a thread group
+ * - shared by CLONE_THREAD
+ */
+#ifdef CONFIG_KEYS
+struct thread_group_cred {
+	atomic_t	usage;
+	pid_t		tgid;			/* thread group process ID */
+	spinlock_t	lock;
+	struct key	*session_keyring;	/* keyring inherited over fork */
+	struct key	*process_keyring;	/* keyring private to this process */
+	struct rcu_head	rcu;			/* RCU deletion hook */
+};
+#endif
+
+/*
+ * 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 */
+	struct thread_group_cred *tgcred; /* thread-group shared credentials */
+#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 */
+};
+
+extern void __put_cred(struct cred *);
+extern int copy_creds(struct task_struct *, unsigned long);
+extern struct cred *prepare_creds(void);
+extern struct cred *prepare_exec_creds(void);
+extern struct cred *prepare_usermodehelper_creds(void);
+extern int commit_creds(struct cred *);
+extern void abort_creds(struct cred *);
+extern const struct cred *override_creds(const struct cred *);
+extern void revert_creds(const struct cred *);
+extern struct cred *prepare_kernel_cred(struct task_struct *);
+extern int change_create_files_as(struct cred *, struct inode *);
+extern int set_security_override(struct cred *, u32);
+extern int set_security_override_from_ctx(struct cred *, const char *);
+extern int set_create_files_as(struct cred *, struct inode *);
+extern void __init cred_init(void);
+
+/**
+ * get_new_cred - Get a reference on a new set of credentials
+ * @cred: The new credentials to reference
+ *
+ * Get a reference on the specified set of new credentials.  The caller must
+ * release the reference.
+ */
+static inline struct cred *get_new_cred(struct cred *cred)
+{
+	atomic_inc(&cred->usage);
+	return cred;
+}
+
+/**
+ * get_cred - Get a reference on a set of credentials
+ * @cred: The credentials to reference
+ *
+ * Get a reference on the specified set of credentials.  The caller must
+ * release the reference.
+ *
+ * This is used to deal with a committed set of credentials.  Although the
+ * pointer is const, this will temporarily discard the const and increment the
+ * usage count.  The purpose of this is to attempt to catch at compile time the
+ * accidental alteration of a set of credentials that should be considered
+ * immutable.
+ */
+static inline const struct cred *get_cred(const struct cred *cred)
+{
+	return get_new_cred((struct cred *) cred);
+}
+
+/**
+ * put_cred - Release a reference to a set of credentials
+ * @cred: The credentials to release
+ *
+ * Release a reference to a set of credentials, deleting them when the last ref
+ * is released.
+ *
+ * This takes a const pointer to a set of credentials because the credentials
+ * on task_struct are attached by const pointers to prevent accidental
+ * alteration of otherwise immutable credential sets.
+ */
+static inline void put_cred(const struct cred *_cred)
+{
+	struct cred *cred = (struct cred *) _cred;
+
+	BUG_ON(atomic_read(&(cred)->usage) <= 0);
+	if (atomic_dec_and_test(&(cred)->usage))
+		__put_cred(cred);
+}
+
+/**
+ * current_cred - Access the current task's subjective credentials
+ *
+ * Access the subjective credentials of the current task.
+ */
+#define current_cred() \
+	(current->cred)
+
+/**
+ * __task_cred - Access a task's objective credentials
+ * @task: The task to query
+ *
+ * Access the objective credentials of a task.  The caller must hold the RCU
+ * readlock.
+ *
+ * The caller must make sure task doesn't go away, either by holding a ref on
+ * task or by holding tasklist_lock to prevent it from being unlinked.
+ */
+#define __task_cred(task) \
+	((const struct cred *)(rcu_dereference((task)->real_cred)))
+
+/**
+ * get_task_cred - Get another task's objective credentials
+ * @task: The task to query
+ *
+ * Get the objective credentials of a task, pinning them so that they can't go
+ * away.  Accessing a task's credentials directly is not permitted.
+ *
+ * The caller must make sure task doesn't go away, either by holding a ref on
+ * task or by holding tasklist_lock to prevent it from being unlinked.
+ */
+#define get_task_cred(task)				\
+({							\
+	struct cred *__cred;				\
+	rcu_read_lock();				\
+	__cred = (struct cred *) __task_cred((task));	\
+	get_cred(__cred);				\
+	rcu_read_unlock();				\
+	__cred;						\
+})
+
+/**
+ * get_current_cred - Get the current task's subjective credentials
+ *
+ * Get the subjective credentials of the current task, pinning them so that
+ * they can't go away.  Accessing the current task's credentials directly is
+ * not permitted.
+ */
+#define get_current_cred()				\
+	(get_cred(current_cred()))
+
+/**
+ * get_current_user - Get the current task's user_struct
+ *
+ * Get the user record of the current task, pinning it so that it can't go
+ * away.
+ */
+#define get_current_user()				\
+({							\
+	struct user_struct *__u;			\
+	struct cred *__cred;				\
+	__cred = (struct cred *) current_cred();	\
+	__u = get_uid(__cred->user);			\
+	__u;						\
+})
+
+/**
+ * get_current_groups - Get the current task's supplementary group list
+ *
+ * Get the supplementary group list of the current task, pinning it so that it
+ * can't go away.
+ */
+#define get_current_groups()				\
+({							\
+	struct group_info *__groups;			\
+	struct cred *__cred;				\
+	__cred = (struct cred *) current_cred();	\
+	__groups = get_group_info(__cred->group_info);	\
+	__groups;					\
+})
+
+#define task_cred_xxx(task, xxx)			\
+({							\
+	__typeof__(((struct cred *)NULL)->xxx) ___val;	\
+	rcu_read_lock();				\
+	___val = __task_cred((task))->xxx;		\
+	rcu_read_unlock();				\
+	___val;						\
+})
+
+#define task_uid(task)		(task_cred_xxx((task), uid))
+#define task_euid(task)		(task_cred_xxx((task), euid))
+
+#define current_cred_xxx(xxx)			\
+({						\
+	current->cred->xxx;			\
+})
+
+#define current_uid()		(current_cred_xxx(uid))
+#define current_gid()		(current_cred_xxx(gid))
+#define current_euid()		(current_cred_xxx(euid))
+#define current_egid()		(current_cred_xxx(egid))
+#define current_suid()		(current_cred_xxx(suid))
+#define current_sgid()		(current_cred_xxx(sgid))
+#define current_fsuid() 	(current_cred_xxx(fsuid))
+#define current_fsgid() 	(current_cred_xxx(fsgid))
+#define current_cap()		(current_cred_xxx(cap_effective))
+#define current_user()		(current_cred_xxx(user))
+#define current_user_ns()	(current_cred_xxx(user)->user_ns)
+#define current_security()	(current_cred_xxx(security))
 
 #define current_uid_gid(_uid, _gid)		\
 do {						\
-	*(_uid) = current->uid;			\
-	*(_gid) = current->gid;			\
+	const struct cred *__cred;		\
+	__cred = current_cred();		\
+	*(_uid) = __cred->uid;			\
+	*(_gid) = __cred->gid;			\
 } while(0)
 
-#define current_euid_egid(_uid, _gid)		\
+#define current_euid_egid(_euid, _egid)		\
 do {						\
-	*(_uid) = current->euid;		\
-	*(_gid) = current->egid;		\
+	const struct cred *__cred;		\
+	__cred = current_cred();		\
+	*(_euid) = __cred->euid;		\
+	*(_egid) = __cred->egid;		\
 } while(0)
 
-#define current_fsuid_fsgid(_uid, _gid)		\
+#define current_fsuid_fsgid(_fsuid, _fsgid)	\
 do {						\
-	*(_uid) = current->fsuid;		\
-	*(_gid) = current->fsgid;		\
+	const struct cred *__cred;		\
+	__cred = current_cred();		\
+	*(_fsuid) = __cred->fsuid;		\
+	*(_fsgid) = __cred->fsgid;		\
 } while(0)
 
 #endif /* _LINUX_CRED_H */