From: Qianli Zhao <zhaoqia...@xiaomi.com>
Once any init thread finds SIGNAL_GROUP_EXIT, trigger panic immediately
instead of last thread of global init has exited, and do not allow other
init threads to exit, protect task/memory state of all sub-threads for
get reliable init coredump
[ 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 <zhaoqia...@xiaomi.com>
---
We got an init crash issue, but we can't get init coredump from fulldump, we
also
see BUG() triggered which calling in zap_pid_ns_processes().
>From crash dump we can get the following information:
1. "Attempted to kill init",init process is killed.
- Kernel panic - not syncing: Attempted to kill init! exitcode=0x00007f00
2. At the same time as init crash, a BUG() triggered in other core.
- [ 24.705390] kernel BUG at include/linux/pid_namespace.h:98!
3. When init thread calls exit_mm, the corresponding thread task->mm will be
empty, which is not conducive to extracting coredump
To fix the issue and save complete coredump, once find init thread is set to
SIGNAL_GROUP_EXIT
trigger panic immediately,and other child threads are not allowed to exit just
wait for reboot
PID: 1 TASK: ffffffc973126900 CPU: 7 COMMAND: "init"
#0 [ffffff800805ba60] perf_trace_kernel_panic_late at ffffff99ac0bcbcc
#1 [ffffff800805bac0] die at ffffff99ac08dc64
#2 [ffffff800805bb10] bug_handler at ffffff99ac08e398
#3 [ffffff800805bbc0] brk_handler at ffffff99ac08529c
#4 [ffffff800805bc80] do_debug_exception at ffffff99ac0814e4
#5 [ffffff800805bdf0] el1_dbg at ffffff99ac083298
->Exception
/home/work/courbet-r-stable-build/kernel/msm-4.14/include/linux/pid_namespace.h:
98
#6 [ffffff800805be20] do_exit at ffffff99ac0c22e8
#7 [ffffff800805be80] do_group_exit at ffffff99ac0c2658
#8 [ffffff800805beb0] sys_exit_group at ffffff99ac0c266c
#9 [ffffff800805bff0] el0_svc_naked at ffffff99ac083cf
->SYSCALLNO: 5e (__NR_exit_group)
PID: 552 TASK: ffffffc9613c8f00 CPU: 4 COMMAND: "init"
#0 [ffffff801455b870] __delay at ffffff99ad32cc14
#1 [ffffff801455b8b0] __const_udelay at ffffff99ad32cd10
#2 [ffffff801455b8c0] msm_trigger_wdog_bite at ffffff99ac5d5be0
#3 [ffffff801455b980] do_msm_restart at ffffff99acccc3f8
#4 [ffffff801455b9b0] machine_restart at ffffff99ac085dd0
#5 [ffffff801455b9d0] emergency_restart at ffffff99ac0eb6dc
#6 [ffffff801455baf0] panic at ffffff99ac0bd008
#7 [ffffff801455bb70] do_exit at ffffff99ac0c257c
/home/work/courbet-r-stable-build/kernel/msm-4.14/kernel/exit.c: 842
#8 [ffffff801455bbd0] do_group_exit at ffffff99ac0c2644
#9 [ffffff801455bcc0] get_signal at ffffff99ac0d1384
#10 [ffffff801455be60] do_notify_resume at ffffff99ac08b2a8
#11 [ffffff801455bff0] work_pending at ffffff99ac083b8c
---
kernel/exit.c | 29 +++++++++++++++++++++--------
1 file changed, 21 insertions(+), 8 deletions(-)
diff --git a/kernel/exit.c b/kernel/exit.c
index ef2fb929..6b2da22 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -758,6 +758,27 @@ void __noreturn do_exit(long code)
validate_creds_for_do_exit(tsk);
/*
+ * Once init group is marked for death,
+ * panic immediately to get a useable coredump
+ */
+ if (unlikely(is_global_init(tsk) &&
+ signal_group_exit(tsk->signal))) {
+ spin_lock_irq(&tsk->sighand->siglock);
+ if (!(tsk->signal->flags & SIGNAL_UNKILLABLE)) {
+ tsk->signal->flags |= SIGNAL_UNKILLABLE;
+ spin_unlock_irq(&tsk->sighand->siglock);
+ panic("Attempted to kill init! exitcode=0x%08x\n",
+ tsk->signal->group_exit_code ?: (int)code);
+ } else {
+ /* init sub-thread is dying, just wait for reboot */
+ spin_unlock_irq(&tsk->sighand->siglock);
+ futex_exit_recursive(tsk);
+ set_current_state(TASK_UNINTERRUPTIBLE);
+ schedule();
+ }
+ }
+
+ /*
* We're taking recursive faults here in do_exit. Safest is to just
* leave this task alone and wait for reboot.
*/
@@ -776,14 +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
