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 */