audit: Make testing for a valid loginuid explicit.

audit rule additions containing "-F auid!=4294967295" were failing
with EINVAL because of a regression caused by e1760bd.

Apparently some userland audit rule sets want to know if loginuid uid
has been set and are using a test for auid != 4294967295 to determine
that.

In practice that is a horrible way to ask if a value has been set,
because it relies on subtle implementation details and will break
every time the uid implementation in the kernel changes.

So add a clean way to test if the audit loginuid has been set, and
silently convert the old idiom to the cleaner and more comprehensible
new idiom.

Cc: <stable@vger.kernel.org> # 3.7
Reported-By: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Tested-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Eric Paris <eparis@redhat.com>

diff --git a/include/linux/audit.h b/include/linux/audit.h
index 469d117..b20b038 100644 (file)
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -391,6 +391,11 @@ static inline void audit_ptrace(struct task_struct *t)
 #define audit_signals 0
 #endif /* CONFIG_AUDITSYSCALL */
 
+static inline bool audit_loginuid_set(struct task_struct *tsk)
+{
+       return uid_valid(audit_get_loginuid(tsk));
+}
+
 #ifdef CONFIG_AUDIT
 /* These are defined in audit.c */
                                /* Public API */

diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index c058c24..75cef3f 100644 (file)
--- a/include/uapi/linux/audit.h
+++ b/include/uapi/linux/audit.h
@@ -246,6 +246,7 @@
 #define AUDIT_OBJ_TYPE 21
 #define AUDIT_OBJ_LEV_LOW      22
 #define AUDIT_OBJ_LEV_HIGH     23
+#define AUDIT_LOGINUID_SET     24
 
                                /* These are ONLY useful when checking
                                 * at syscall exit time (AUDIT_AT_EXIT). */

diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c
index 478f460..bc6595f 100644 (file)
--- a/kernel/auditfilter.c
+++ b/kernel/auditfilter.c
@@ -365,7 +365,10 @@ static int audit_field_valid(struct audit_entry *entry, struct audit_field *f)
        case AUDIT_DIR:
        case AUDIT_FILTERKEY:
                break;
-       /* arch is only allowed to be = or != */
+       case AUDIT_LOGINUID_SET:
+               if ((f->val != 0) && (f->val != 1))
+                       return -EINVAL;
+       /* FALL THROUGH */
        case AUDIT_ARCH:
                if (f->op != Audit_not_equal && f->op != Audit_equal)
                        return -EINVAL;
@@ -419,17 +422,23 @@ static struct audit_entry *audit_data_to_entry(struct audit_rule_data *data,
                f->lsm_str = NULL;
                f->lsm_rule = NULL;
 
+               /* Support legacy tests for a valid loginuid */
+               if ((f->type == AUDIT_LOGINUID) && (f->val == 4294967295)) {
+                       f->type = AUDIT_LOGINUID_SET;
+                       f->val = 0;
+               }
+
                err = audit_field_valid(entry, f);
                if (err)
                        goto exit_free;
 
                err = -EINVAL;
                switch (f->type) {
+               case AUDIT_LOGINUID:
                case AUDIT_UID:
                case AUDIT_EUID:
                case AUDIT_SUID:
                case AUDIT_FSUID:
-               case AUDIT_LOGINUID:
                case AUDIT_OBJ_UID:
                        f->uid = make_kuid(current_user_ns(), f->val);
                        if (!uid_valid(f->uid))
@@ -1222,6 +1231,10 @@ static int audit_filter_user_rules(struct audit_krule *rule, int type,
                        result = audit_uid_comparator(audit_get_loginuid(current),
                                                  f->op, f->uid);
                        break;
+               case AUDIT_LOGINUID_SET:
+                       result = audit_comparator(audit_loginuid_set(current),
+                                                 f->op, f->val);
+                       break;
                case AUDIT_MSGTYPE:
                        result = audit_comparator(type, f->op, f->val);
                        break;

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index add3086..3c8a601 100644 (file)
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -613,6 +613,9 @@ static int audit_filter_rules(struct task_struct *tsk,
                        if (ctx)
                                result = audit_uid_comparator(tsk->loginuid, f->op, f->uid);
                        break;
+               case AUDIT_LOGINUID_SET:
+                       result = audit_comparator(audit_loginuid_set(tsk), f->op, f->val);
+                       break;
                case AUDIT_SUBJ_USER:
                case AUDIT_SUBJ_ROLE:
                case AUDIT_SUBJ_TYPE:
@@ -1970,7 +1973,7 @@ int audit_set_loginuid(kuid_t loginuid)
        unsigned int sessionid;
 
 #ifdef CONFIG_AUDIT_LOGINUID_IMMUTABLE
-       if (uid_valid(task->loginuid))
+       if (audit_loginuid_set(task))
                return -EPERM;
 #else /* CONFIG_AUDIT_LOGINUID_IMMUTABLE */
        if (!capable(CAP_AUDIT_CONTROL))