diff options
| -rw-r--r-- | kernel/events/core.c | 58 |
1 files changed, 32 insertions, 26 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c index c13730b7ac01..1cb1f9b8392e 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -11917,6 +11917,37 @@ again: return gctx; } +static bool +perf_check_permission(struct perf_event_attr *attr, struct task_struct *task) +{ + unsigned int ptrace_mode = PTRACE_MODE_READ_REALCREDS; + bool is_capable = perfmon_capable(); + + if (attr->sigtrap) { + /* + * perf_event_attr::sigtrap sends signals to the other task. + * Require the current task to also have CAP_KILL. + */ + rcu_read_lock(); + is_capable &= ns_capable(__task_cred(task)->user_ns, CAP_KILL); + rcu_read_unlock(); + + /* + * If the required capabilities aren't available, checks for + * ptrace permissions: upgrade to ATTACH, since sending signals + * can effectively change the target task. + */ + ptrace_mode = PTRACE_MODE_ATTACH_REALCREDS; + } + + /* + * Preserve ptrace permission check for backwards compatibility. The + * ptrace check also includes checks that the current task and other + * task have matching uids, and is therefore not done here explicitly. + */ + return is_capable || ptrace_may_access(task, ptrace_mode); +} + /** * sys_perf_event_open - open a performance event, associate it to a task/cpu * @@ -12158,43 +12189,18 @@ SYSCALL_DEFINE5(perf_event_open, } if (task) { - unsigned int ptrace_mode = PTRACE_MODE_READ_REALCREDS; - bool is_capable; - err = down_read_interruptible(&task->signal->exec_update_lock); if (err) goto err_file; - is_capable = perfmon_capable(); - if (attr.sigtrap) { - /* - * perf_event_attr::sigtrap sends signals to the other - * task. Require the current task to also have - * CAP_KILL. - */ - rcu_read_lock(); - is_capable &= ns_capable(__task_cred(task)->user_ns, CAP_KILL); - rcu_read_unlock(); - - /* - * If the required capabilities aren't available, checks - * for ptrace permissions: upgrade to ATTACH, since - * sending signals can effectively change the target - * task. - */ - ptrace_mode = PTRACE_MODE_ATTACH_REALCREDS; - } - /* - * Preserve ptrace permission check for backwards compatibility. - * * We must hold exec_update_lock 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 (!is_capable && !ptrace_may_access(task, ptrace_mode)) + if (!perf_check_permission(&attr, task)) goto err_cred; } |