From: chenqiwu chenqiwu@xiaomi.com
commit 43cf75d96409a20ef06b756877a2e72b10a026fc upstream.
Currently, when global init and all threads in its thread-group have exited we panic via: do_exit() -> exit_notify() -> forget_original_parent() -> find_child_reaper() This makes it hard to extract a useable coredump for global init from a kernel crashdump because by the time we panic exit_mm() will have already released global init's mm. This patch moves the panic futher up before exit_mm() is called. As was the case previously, we only panic when global init and all its threads in the thread-group have exited.
Signed-off-by: chenqiwu chenqiwu@xiaomi.com Acked-by: Christian Brauner christian.brauner@ubuntu.com Acked-by: Oleg Nesterov oleg@redhat.com [christian.brauner@ubuntu.com: fix typo, rewrite commit message] Link: https://lore.kernel.org/r/1576736993-10121-1-git-send-email-qiwuchen55@gmail... Signed-off-by: Christian Brauner christian.brauner@ubuntu.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/exit.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
--- a/kernel/exit.c +++ b/kernel/exit.c @@ -578,10 +578,6 @@ static struct task_struct *find_child_re }
write_unlock_irq(&tasklist_lock); - if (unlikely(pid_ns == &init_pid_ns)) { - panic("Attempted to kill init! exitcode=0x%08x\n", - father->signal->group_exit_code ?: father->exit_code); - }
list_for_each_entry_safe(p, n, dead, ptrace_entry) { list_del_init(&p->ptrace_entry); @@ -845,6 +841,14 @@ 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);