linux-kernel - [PATCH] exit: Detect and fix irq disabled state in oops

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Message-Id: <20230120011820.2664120-1-npiggin@gmail.com>
Date:   Fri, 20 Jan 2023 11:18:20 +1000
From:   Nicholas Piggin <npiggin@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Nicholas Piggin <npiggin@...il.com>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        Michael Ellerman <mpe@...erman.id.au>,
        "Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [PATCH] exit: Detect and fix irq disabled state in oops

If a task oopses with irqs disabled, this can cause various cascading
problems in the oops path such as sleep-from-invalid warnings, and
potentially worse.

Since commit 0258b5fd7c712 ("coredump: Limit coredumps to a single
thread group"), the unconditional irq enable in coredump_task_exit()
will "fix" the irq state to be enabled early in do_exit(), so currently
this may not be triggerable, but that is coincidental and fragile.

Detect and fix the irqs_disabled() condition in the oops path before
calling do_exit(), similarly to the way in_atomic() is handled.

Link: https://lore.kernel.org/lkml/20221004094401.708299-1-npiggin@gmail.com/
Reported-by: Michael Ellerman <mpe@...erman.id.au>
Acked-by: "Eric W. Biederman" <ebiederm@...ssion.com>
Signed-off-by: Nicholas Piggin <npiggin@...il.com>
---
Hi Peter,

Would you consider taking this through the sched tree?

Thanks,
Nick

 kernel/exit.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/exit.c b/kernel/exit.c
index 15dc2ec80c46..bccfa4218356 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -807,6 +807,8 @@ void __noreturn do_exit(long code)
 	struct task_struct *tsk = current;
 	int group_dead;
 
+	WARN_ON(irqs_disabled());
+
 	synchronize_group_exit(tsk, code);
 
 	WARN_ON(tsk->plug);
@@ -938,6 +940,11 @@ void __noreturn make_task_dead(int signr)
 	if (unlikely(!tsk->pid))
 		panic("Attempted to kill the idle task!");
 
+	if (unlikely(irqs_disabled())) {
+		pr_info("note: %s[%d] exited with irqs disabled\n",
+			current->comm, task_pid_nr(current));
+		local_irq_enable();
+	}
 	if (unlikely(in_atomic())) {
 		pr_info("note: %s[%d] exited with preempt_count %d\n",
 			current->comm, task_pid_nr(current),
-- 
2.37.2