Messages in this thread Patch in this message | | | From | Qianli Zhao <> | Subject | [PATCH V2] exit: trigger panic when global init has exited | Date | Fri, 12 Mar 2021 11:24:38 +0800 |
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From: Qianli Zhao <zhaoqianli@xiaomi.com>
When init sub-threads running on different CPUs exit at the same time, zap_pid_ns_processe()->BUG() may be happened. And every thread status is abnormal after exit(PF_EXITING set,task->mm=NULL etc), which makes it difficult to parse coredump from fulldump normally. In order to fix the above problem, when any one init has been set to SIGNAL_GROUP_EXIT, trigger panic immediately, and prevent other init threads from continuing to exit.
[ 24.705376] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00007f00 [ 24.705382] CPU: 4 PID: 552 Comm: init Tainted: G S O 4.14.180-perf-g4483caa8ae80-dirty #1 [ 24.705390] kernel BUG at include/linux/pid_namespace.h:98!
PID: 552 CPU: 4 COMMAND: "init" PID: 1 CPU: 7 COMMAND: "init" core4 core7 ... sys_exit_group() do_group_exit() - sig->flags = SIGNAL_GROUP_EXIT - zap_other_threads() do_exit() //PF_EXITING is set ret_to_user() do_notify_resume() get_signal() - signal_group_exit - goto fatal; do_group_exit() do_exit() //PF_EXITING is set - panic("Attempted to kill init! exitcode=0x%08x\n") exit_notify() find_alive_thread() //no alive sub-threads zap_pid_ns_processes()//CONFIG_PID_NS is not set BUG()
Signed-off-by: Qianli Zhao <zhaoqianli@xiaomi.com> --- V2: - Changelog update - Remove wrong useage of SIGNAL_UNKILLABLE. - Add thread_group_empty() test to handle single init thread exit
--- kernel/exit.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-)
diff --git a/kernel/exit.c b/kernel/exit.c index 04029e3..9d2716b 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -767,6 +767,17 @@ void __noreturn do_exit(long code) validate_creds_for_do_exit(tsk); /* + * If global init has exited, + * panic immediately to get a useable coredump. + */ + if (unlikely(is_global_init(tsk) && + (thread_group_empty(tsk) || + (tsk->signal->flags & SIGNAL_GROUP_EXIT)))) { + panic("Attempted to kill init! exitcode=0x%08x\n", + tsk->signal->group_exit_code ?: (int)code); + } + + /* * We're taking recursive faults here in do_exit. Safest is to just * leave this task alone and wait for reboot. */ @@ -786,14 +797,6 @@ void __noreturn do_exit(long code) acct_update_integrals(tsk); group_dead = atomic_dec_and_test(&tsk->signal->live); if (group_dead) { - /* - * If the last thread of global init has exited, panic - * immediately to get a useable coredump. - */ - if (unlikely(is_global_init(tsk))) - panic("Attempted to kill init! exitcode=0x%08x\n", - tsk->signal->group_exit_code ?: (int)code); - #ifdef CONFIG_POSIX_TIMERS hrtimer_cancel(&tsk->signal->real_timer); exit_itimers(tsk->signal); -- 1.9.1
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