[PATCH] get rid of loginuid races

Keeping loginuid in audit_context is racy and results in messier
code.  Taken to task_struct, out of the way of ->audit_context
changes.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 15 insertions, 41 deletions

diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index bd4e0a2443fb..c95173a194bf 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -192,7 +192,6 @@ struct audit_context {
         enum audit_state    state;
         unsigned int        serial;     /* serial number for record */
         struct timespec     ctime;      /* time of syscall entry */
-        uid_t               loginuid;   /* login uid (identity) */
         int                 major;      /* syscall number */
         unsigned long       argv[4];    /* syscall arguments */
         int                 return_valid; /* return code is valid */
@@ -506,7 +505,7 @@ static int audit_filter_rules(struct task_struct *tsk,
                 case AUDIT_LOGINUID:
                         result = 0;
                         if (ctx)
-                                result = audit_comparator(ctx->loginuid, f->op, f->val);
+                                result = audit_comparator(tsk->loginuid, f->op, f->val);
                         break;
                 case AUDIT_SUBJ_USER:
                 case AUDIT_SUBJ_ROLE:
@@ -783,11 +782,8 @@ static inline void audit_free_aux(struct audit_context *context)
 static inline void audit_zero_context(struct audit_context *context,
                                       enum audit_state state)
 {
-        uid_t loginuid = context->loginuid;
-
         memset(context, 0, sizeof(*context));
         context->state      = state;
-        context->loginuid   = loginuid;
 }
 
 static inline struct audit_context *audit_alloc_context(enum audit_state state)
@@ -826,11 +822,6 @@ int audit_alloc(struct task_struct *tsk)
                 return -ENOMEM;
         }
 
-                                /* Preserve login uid */
-        context->loginuid = -1;
-        if (current->audit_context)
-                context->loginuid = current->audit_context->loginuid;
-
         tsk->audit_context  = context;
         set_tsk_thread_flag(tsk, TIF_SYSCALL_AUDIT);
         return 0;
@@ -1047,7 +1038,7 @@ static void audit_log_exit(struct audit_context *context, struct task_struct *ts
                   context->name_count,
                   context->ppid,
                   context->pid,
-                  context->loginuid,
+                  tsk->loginuid,
                   context->uid,
                   context->gid,
                   context->euid, context->suid, context->fsuid,
@@ -1779,40 +1770,23 @@ int audit_set_loginuid(struct task_struct *task, uid_t loginuid)
 {
         struct audit_context *context = task->audit_context;
 
-        if (context) {
-                /* Only log if audit is enabled */
-                if (context->in_syscall) {
-                        struct audit_buffer *ab;
-
-                        ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_LOGIN);
-                        if (ab) {
-                                audit_log_format(ab, "login pid=%d uid=%u "
-                                        "old auid=%u new auid=%u",
-                                        task->pid, task->uid,
-                                        context->loginuid, loginuid);
-                                audit_log_end(ab);
-                        }
+        if (context && context->in_syscall) {
+                struct audit_buffer *ab;
+
+                ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_LOGIN);
+                if (ab) {
+                        audit_log_format(ab, "login pid=%d uid=%u "
+                                "old auid=%u new auid=%u",
+                                task->pid, task->uid,
+                                task->loginuid, loginuid);
+                        audit_log_end(ab);
                 }
-                context->loginuid = loginuid;
         }
+        task->loginuid = loginuid;
         return 0;
 }
 
 /**
- * audit_get_loginuid - get the loginuid for an audit_context
- * @ctx: the audit_context
- *
- * Returns the context's loginuid or -1 if @ctx is NULL.
- */
-uid_t audit_get_loginuid(struct task_struct *task)
-{
-        struct audit_context *ctx = task->audit_context;
-        return ctx ? ctx->loginuid : -1;
-}
-
-EXPORT_SYMBOL(audit_get_loginuid);
-
-/**
  * __audit_mq_open - record audit data for a POSIX MQ open
  * @oflag: open flag
  * @mode: mode bits
@@ -2217,8 +2191,8 @@ int __audit_signal_info(int sig, struct task_struct *t)
         if (audit_pid && t->tgid == audit_pid) {
                 if (sig == SIGTERM || sig == SIGHUP || sig == SIGUSR1) {
                         audit_sig_pid = tsk->pid;
-                        if (ctx)
-                                audit_sig_uid = ctx->loginuid;
+                        if (tsk->loginuid != -1)
+                                audit_sig_uid = tsk->loginuid;
                         else
                                 audit_sig_uid = tsk->uid;
                         selinux_get_task_sid(tsk, &audit_sig_sid);