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Message-ID: <ee98e3a4-8664-ea20-dd9a-eff5edbe8a9e@linux.microsoft.com>
Date: Mon, 30 Dec 2019 10:37:30 -0800
From: Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
To: Mimi Zohar <zohar@...ux.ibm.com>,
kernel test robot <rong.a.chen@...el.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
Mimi Zohar <zohar@...ux.vnet.ibm.com>,
linux-integrity@...r.kernel.org, lkp@...ts.01.org
Subject: Re: [IMA] 11b771ffff:
BUG:sleeping_function_called_from_invalid_context_at_kernel/locking/mutex.c
On 12/30/19 9:01 AM, Mimi Zohar wrote:
Hi Mimi,
> Hi Lakshmi,
>
> On Fri, 2019-12-27 at 22:23 +0800, kernel test robot wrote:
>> [ 333.455345] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:281
>> [ 333.457243] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 12395, name: userfaultfd
>> [ 333.458888] CPU: 1 PID: 12395 Comm: userfaultfd Not tainted 5.5.0-rc1-00011-g11b771ffff8fc #1
>> [ 333.461096] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
>> [ 333.463893] Call Trace:
>> [ 333.465287] <IRQ>
>> [ 333.466351] dump_stack+0x66/0x8b
>> [ 333.467346] ___might_sleep+0x102/0x120
>> [ 333.468385] mutex_lock+0x1c/0x40
>> [ 333.469421] ima_process_queued_keys+0x24/0x110
>> [ 333.470529] ? ima_process_queued_keys+0x110/0x110
>> [ 333.471656] call_timer_fn+0x2d/0x140
>> [ 333.472707] run_timer_softirq+0x46f/0x4b0
>> [ 333.473752] ? enqueue_hrtimer+0x39/0xa0
>> [ 333.474780] __do_softirq+0xe3/0x2f8
>> [ 333.475768] irq_exit+0xd5/0xe0
>> [ 333.476738] smp_apic_timer_interrupt+0x74/0x140
>> [ 333.477834] apic_timer_interrupt+0xf/0x20
>> [ 333.478858] </IRQ>
>
> I think this is an instance where defining timer_expired as atomic and
> then testing it using atomic_dec_and_test() would help. Either the
> queued keys would be deleted in ima_timer_handler() or measured in
> ima_process_queued_keys().
>
> Mimi
Would it be better to use a spinlock (instead of a mutex) to synchronize
access to the queued keys list? That would work for timer callback
function also.
Before submitting the patch for freeing the keys I had tested the case
where queued keys are freed in timer callback. But I did not hit the
above break.
I will follow the steps given by Rong and validate the fix.
thanks,
-lakshmi
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