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Date: Tue, 10 Apr 2018 16:50:51 -0400
From: Joe Lawrence <joe.lawrence@...hat.com>
To: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: live-patching@...r.kernel.org, linux-kselftest@...r.kernel.org,
linux-kernel@...r.kernel.org, Jiri Kosina <jikos@...nel.org>,
Petr Mladek <pmladek@...e.com>,
Miroslav Benes <mbenes@...e.cz>,
Libor Pecháček <lpechacek@...e.com>,
Nicolai Stange <nstange@...e.de>,
Artem Savkov <asavkov@...hat.com>
Subject: Re: [PATCH v2] selftests/livepatch: introduce tests
On 04/10/2018 04:00 PM, Josh Poimboeuf wrote:
> On Tue, Apr 10, 2018 at 11:15:54AM -0400, Joe Lawrence wrote:
>> +static void test_klp_shadow_vars_exit(void)
>> +{
>> +}
>> +
>> +module_init(test_klp_shadow_vars_init);
>> +module_init(test_klp_shadow_vars_exit);
>
> For this last line, s/module_init/module_exit/, though I think the exit
> function can just be removed altogether?
D'oh workspace / git user error, I posted an older version :(
But the exit function seems to be required if an init function is
provided. Here I omitted the exit function:
% modprobe test_klp_shadow_vars
% lsmod | grep test_klp_shadow_vars
test_klp_shadow_vars 16384 0
% rmmod test_klp_shadow_vars
rmmod: ERROR: could not remove 'test_klp_shadow_vars': Device or
resource busy
rmmod: ERROR: could not remove module test_klp_shadow_vars: Device or
resource busy
and from kernel/module.c
SYSCALL_DEFINE2(delete_module, const char __user *, name_user,
unsigned int, flags)
...
/* If it has an init func, it must have an exit func to unload*/
if (mod->init && !mod->exit) {
forced = try_force_unload(flags);
if (!forced) {
/* This module can't be removed */
ret = -EBUSY;
goto out;
}
}
...
>
> Also I get the following bug (run on latest Linus master + Petr's two
> patch sets):
>
> [ 106.302072] % modprobe test_klp_shadow_vars
> [ 106.311165] test_klp_shadow_vars: klp_shadow_get(obj=PTR5, id=0x1234) = PTR0
> [ 106.313080] test_klp_shadow_vars: got expected NULL result
> [ 106.314811] BUG: sleeping function called from invalid context at mm/slab.h:421
> [ 106.316518] in_atomic(): 1, irqs_disabled(): 1, pid: 2254, name: modprobe
> [ 106.318107] 1 lock held by modprobe/2254:
> [ 106.319332] #0: 00000000d0851080 (klp_shadow_lock){....}, at: __klp_shadow_get_or_alloc+0x88/0x1b0
> [ 106.321220] irq event stamp: 4408
> [ 106.322176] hardirqs last enabled at (4407): [<ffffffff8114c28e>] console_unlock+0x44e/0x680
> [ 106.323598] hardirqs last disabled at (4408): [<ffffffff8199e6c7>] _raw_spin_lock_irqsave+0x27/0x90
> [ 106.325041] softirqs last enabled at (4404): [<ffffffff81c0039b>] __do_softirq+0x39b/0x4fc
> [ 106.326469] softirqs last disabled at (4367): [<ffffffff810d8450>] irq_exit+0xe0/0xf0
> [ 106.327901] Preemption disabled at:
> [ 106.327905] [<ffffffff81167c28>] __klp_shadow_get_or_alloc+0x88/0x1b0
> [ 106.330117] CPU: 7 PID: 2254 Comm: modprobe Tainted: G K 4.16.0+ #60
> [ 106.331565] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-2.fc27 04/01/2014
> [ 106.333143] Call Trace:
> [ 106.334011] dump_stack+0x8e/0xd5
> [ 106.334962] ___might_sleep+0x185/0x260
> [ 106.335997] ? shadow_dtor+0x40/0x40 [test_klp_shadow_vars]
> [ 106.337170] __might_sleep+0x4a/0x80
> [ 106.338137] kmem_cache_alloc_trace+0x20b/0x300
> [ 106.339183] ? ptr_id+0x5c/0xd0 [test_klp_shadow_vars]
> [ 106.340341] ? shadow_dtor+0x40/0x40 [test_klp_shadow_vars]
> [ 106.341506] ptr_id+0x5c/0xd0 [test_klp_shadow_vars]
> [ 106.342725] shadow_ctor+0x20/0x40 [test_klp_shadow_vars]
> [ 106.343998] __klp_shadow_get_or_alloc+0xc4/0x1b0
> [ 106.345184] ? shadow_dtor+0x40/0x40 [test_klp_shadow_vars]
> [ 106.346494] klp_shadow_alloc+0x10/0x20
> [ 106.347583] shadow_alloc+0x28/0xa0 [test_klp_shadow_vars]
> [ 106.348871] ? shadow_free_all+0x40/0x40 [test_klp_shadow_vars]
> [ 106.350200] test_klp_shadow_vars_init+0x96/0x400 [test_klp_shadow_vars]
> [ 106.351646] ? shadow_free_all+0x40/0x40 [test_klp_shadow_vars]
> [ 106.352949] do_one_initcall+0x61/0x37f
> [ 106.353963] ? rcu_read_lock_sched_held+0x79/0x80
> [ 106.355040] ? kmem_cache_alloc_trace+0x29d/0x300
> [ 106.356098] ? do_init_module+0x27/0x213
> [ 106.357090] do_init_module+0x5f/0x213
> [ 106.358047] load_module+0x2815/0x2e70
> [ 106.358992] ? vfs_read+0x12d/0x150
> [ 106.359920] SYSC_finit_module+0xfc/0x120
> [ 106.360870] ? SYSC_finit_module+0xfc/0x120
> [ 106.361839] SyS_finit_module+0xe/0x10
> [ 106.362753] do_syscall_64+0x7e/0x240
> [ 106.363645] entry_SYSCALL_64_after_hwframe+0x42/0xb7
> [ 106.364711] RIP: 0033:0x7f26d0d40b19
> [ 106.365799] RSP: 002b:00007ffee1de19a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
> [ 106.367306] RAX: ffffffffffffffda RBX: 00005636550d54b0 RCX: 00007f26d0d40b19
> [ 106.368573] RDX: 0000000000000000 RSI: 0000563654134186 RDI: 0000000000000003
> [ 106.369950] RBP: 0000563654134186 R08: 0000000000000000 R09: 00005636550d4270
> [ 106.371164] R10: 0000000000000003 R11: 0000000000000246 R12: 0000000000000000
> [ 106.372422] R13: 00005636550d53b0 R14: 0000000000040000 R15: 00005636550d54b0
I missed Petr's commit msg note "that the constructor is called under
klp_shadow_lock." I'll convert the test to use GFP_ATOMIC for this
allocation.
I'll also add CONFIG_PM_SLEEP_DEBUG=y to my test VM kernel .config. Any
other debug option suggestions?
-- Joe
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