* function.
*
* Lock order:
+ * cred_guard_mutex
* task_struct::perf_event_mutex
* perf_event_context::mutex
* perf_event::child_mutex;
find_lively_task_by_vpid(pid_t vpid)
{
struct task_struct *task;
- int err;
rcu_read_lock();
if (!vpid)
if (!task)
return ERR_PTR(-ESRCH);
- /* Reuse ptrace permission checks for now. */
- err = -EACCES;
- if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS))
- goto errout;
-
return task;
-errout:
- put_task_struct(task);
- return ERR_PTR(err);
-
}
/*
get_online_cpus();
+ if (task) {
+ err = mutex_lock_interruptible(&task->signal->cred_guard_mutex);
+ if (err)
+ goto err_cpus;
+
+ /*
+ * Reuse ptrace permission checks for now.
+ *
+ * We must hold cred_guard_mutex across this and any potential
+ * perf_install_in_context() call for this new event to
+ * serialize against exec() altering our credentials (and the
+ * perf_event_exit_task() that could imply).
+ */
+ err = -EACCES;
+ if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS))
+ goto err_cred;
+ }
+
if (flags & PERF_FLAG_PID_CGROUP)
cgroup_fd = pid;
NULL, NULL, cgroup_fd);
if (IS_ERR(event)) {
err = PTR_ERR(event);
- goto err_cpus;
+ goto err_cred;
}
if (is_sampling_event(event)) {
goto err_context;
}
- if (task) {
- put_task_struct(task);
- task = NULL;
- }
-
/*
* Look up the group leader (we will attach this event to it):
*/
WARN_ON_ONCE(ctx->parent_ctx);
+ /*
+ * This is the point on no return; we cannot fail hereafter. This is
+ * where we start modifying current state.
+ */
+
if (move_group) {
/*
* See perf_event_ctx_lock() for comments on the details
mutex_unlock(&gctx->mutex);
mutex_unlock(&ctx->mutex);
+ if (task) {
+ mutex_unlock(&task->signal->cred_guard_mutex);
+ put_task_struct(task);
+ }
+
put_online_cpus();
mutex_lock(¤t->perf_event_mutex);
*/
if (!event_file)
free_event(event);
+err_cred:
+ if (task)
+ mutex_unlock(&task->signal->cred_guard_mutex);
err_cpus:
put_online_cpus();
err_task:
/*
* When a child task exits, feed back event values to parent events.
+ *
+ * Can be called with cred_guard_mutex held when called from
+ * install_exec_creds().
*/
void perf_event_exit_task(struct task_struct *child)
{