1 files changed, 317 insertions, 23 deletions

diff --git a/include/linux/cred.h b/include/linux/cred.h
index b69222cc1fd2..26c1ab179946 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 +12,333 @@
 #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 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_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 */