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Date: Thu, 16 Mar 2017 23:23:26 -0600
From: Logan Gunthorpe <logang@...tatee.com>
To: kernel test robot <fengguang.wu@...el.com>
Cc: LKP <lkp@...org>, linux-kernel@...r.kernel.org,
rtc-linux@...glegroups.com,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
wfg@...ux.intel.com
Subject: Re: [rtc] 4cd8adb100: WARNING: CPU: 0 PID: 1 at lib/kobject.c:690
kobject_put
Hey,
I think I see the issue here: in a couple of error conditions, the RTC
code will not initialize and ask for the cdev. However, my change will
always call cdev_add and cdev_del even though the rtc code did not call
cdev_init. I'll have to add a guard around dev->devt in the new
cdev_device functions. I'll prepare another patch tomorrow.
I also noticed that I neglected to remove the prototypes for the two RTC
function I removed. I'll fix that too.
Thanks,
Logan
On 16/03/17 10:57 PM, kernel test robot wrote:
> Greetings,
>
> 0day kernel testing robot got the below dmesg and the first bad commit is
>
> https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git char-misc-testing
>
> commit 4cd8adb100107dc44e63615040ca2bde43de6167
> Author: Logan Gunthorpe <logang@...tatee.com>
> AuthorDate: Mon Mar 6 00:04:30 2017 -0700
> Commit: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> CommitDate: Fri Mar 17 09:20:18 2017 +0900
>
> rtc: utilize new cdev_device_add helper function
>
> Mostly straightforward, but we had to remove the rtc_dev_add/del_device
> functions as they split up the cdev_add and the device_add.
>
> Doing this also revealed that there was likely another subtle bug:
> seeing cdev_add was done after device_register, the cdev probably
> was not ready before device_add when the uevent occurs. This would
> race with userspace, if it tried to use the device directly after
> the uevent. This is fixed just by using the new helper function.
>
> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
> Acked-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>
> c65bbfc122 rapidio: utilize new cdev_device_add helper function
> 4cd8adb100 rtc: utilize new cdev_device_add helper function
> 64d77f61c0 auxdisplay: Add HD44780 Character LCD support
> +-----------------------------------------------------+------------+------------+------------+
> | | c65bbfc122 | 4cd8adb100 | 64d77f61c0 |
> +-----------------------------------------------------+------------+------------+------------+
> | boot_successes | 4 | 0 | 0 |
> | boot_failures | 55 | 26 | 30 |
> | WARNING:at_arch/x86/mm/dump_pagetables.c:#note_page | 55 | 22 | 24 |
> | WARNING:at_lib/kobject.c:#kobject_put | 0 | 26 | 30 |
> | WARNING:at_lib/refcount.c:#refcount_sub_and_test | 0 | 26 | 30 |
> +-----------------------------------------------------+------------+------------+------------+
>
> [ 1.261325] input: AT Translated Set 2 keyboard as /devices/platform/i8042/serio0/input/input1
> [ 1.263029] wistron_btns: System unknown
> [ 1.263411] usbcore: registered new interface driver yealink
> [ 1.264581] rtc-test rtc-test.0: rtc core: registered test as rtc0
> [ 1.265355] ------------[ cut here ]------------
> [ 1.265798] WARNING: CPU: 0 PID: 1 at lib/kobject.c:690 kobject_put+0x39/0x60
> [ 1.266539] kobject: '(null)' (cea81ab4): is not initialized, yet kobject_put() is being called.
> [ 1.267291] Modules linked in:
> [ 1.267562] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.11.0-rc2-00049-g4cd8adb #834
> [ 1.268236] Call Trace:
> [ 1.268453] dump_stack+0x76/0xa9
> [ 1.268740] __warn+0xdb/0x100
> [ 1.269005] ? kobject_put+0x39/0x60
> [ 1.269318] warn_slowpath_fmt+0x36/0x40
> [ 1.269653] kobject_put+0x39/0x60
> [ 1.269948] cdev_del+0x1d/0x20
> [ 1.270224] cdev_device_del+0x14/0x20
> [ 1.270548] rtc_device_unregister+0x2a/0x50
> [ 1.270913] devm_rtc_device_release+0xa/0x10
> [ 1.271291] release_nodes+0x1e4/0x210
> [ 1.271613] devres_release_all+0x51/0x60
> [ 1.271962] driver_probe_device+0x237/0x480
> [ 1.272332] ? klist_next+0x1b/0xc0
> [ 1.272633] ? acpi_driver_match_device+0x49/0x62
> [ 1.273034] __device_attach_driver+0xe8/0x110
> [ 1.273418] ? klist_next+0x9d/0xc0
> [ 1.273718] ? __driver_attach+0xf0/0xf0
> [ 1.274053] bus_for_each_drv+0x44/0x80
> [ 1.274389] __device_attach+0x9d/0x140
> [ 1.274718] ? __driver_attach+0xf0/0xf0
> [ 1.275054] device_initial_probe+0xd/0x10
> [ 1.275409] bus_probe_device+0x25/0x80
> [ 1.275738] device_add+0x3fc/0x5c0
> [ 1.276038] ? kobject_set_name_vargs+0x7f/0xa0
> [ 1.276428] platform_device_add+0x1d9/0x250
> [ 1.276793] test_init+0x52/0xa6
> [ 1.277085] ? stk17ta8_rtc_driver_init+0x11/0x11
> [ 1.277504] do_one_initcall+0x92/0x160
> [ 1.277844] ? parameq+0x13/0x70
> [ 1.278138] ? repair_env_string+0x12/0x51
> [ 1.278500] ? parse_args+0x325/0x470
> [ 1.278826] ? __usermodehelper_set_disable_depth+0x3e/0x50
> [ 1.279318] kernel_init_freeable+0xfb/0x19a
> [ 1.279696] ? do_early_param+0x7a/0x7a
> [ 1.280036] ? rest_init+0x130/0x130
> [ 1.280359] kernel_init+0xb/0x100
> [ 1.280665] ? schedule_tail+0xc/0x60
> [ 1.280991] ? rest_init+0x130/0x130
> [ 1.281314] ret_from_fork+0x21/0x2c
> [ 1.281706] ---[ end trace e98f47d52e9cf212 ]---
> [ 1.282142] ------------[ cut here ]------------
> [ 1.282142] ------------[ cut here ]------------
> [ 1.282555] WARNING: CPU: 0 PID: 1 at lib/refcount.c:128 refcount_sub_and_test+0x55/0xa0
> [ 1.283396] refcount_t: underflow; use-after-free.
> [ 1.283829] Modules linked in:
> [ 1.284110] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G W 4.11.0-rc2-00049-g4cd8adb #834
> [ 1.284904] Call Trace:
> [ 1.285120] dump_stack+0x76/0xa9
> [ 1.285412] __warn+0xdb/0x100
> [ 1.285678] ? refcount_sub_and_test+0x55/0xa0
> [ 1.286071] warn_slowpath_fmt+0x36/0x40
> [ 1.286423] refcount_sub_and_test+0x55/0xa0
> [ 1.286801] refcount_dec_and_test+0xf/0x20
> [ 1.287177] kobject_put+0x41/0x60
> [ 1.287480] cdev_del+0x1d/0x20
> [ 1.287760] cdev_device_del+0x14/0x20
> [ 1.288101] rtc_device_unregister+0x2a/0x50
> [ 1.288474] devm_rtc_device_release+0xa/0x10
> [ 1.288848] release_nodes+0x1e4/0x210
> [ 1.289174] devres_release_all+0x51/0x60
> [ 1.289518] driver_probe_device+0x237/0x480
> [ 1.289898] ? klist_next+0x1b/0xc0
> [ 1.290214] ? acpi_driver_match_device+0x49/0x62
> [ 1.290628] __device_attach_driver+0xe8/0x110
> [ 1.291021] ? klist_next+0x9d/0xc0
> [ 1.291336] ? __driver_attach+0xf0/0xf0
> [ 1.291684] bus_for_each_drv+0x44/0x80
> [ 1.292024] __device_attach+0x9d/0x140
> [ 1.292369] ? __driver_attach+0xf0/0xf0
> [ 1.292717] device_initial_probe+0xd/0x10
> [ 1.293086] bus_probe_device+0x25/0x80
> [ 1.293421] device_add+0x3fc/0x5c0
> [ 1.293722] ? kobject_set_name_vargs+0x7f/0xa0
> [ 1.294129] platform_device_add+0x1d9/0x250
> [ 1.294510] test_init+0x52/0xa6
> [ 1.294799] ? stk17ta8_rtc_driver_init+0x11/0x11
> [ 1.295217] do_one_initcall+0x92/0x160
> [ 1.295559] ? parameq+0x13/0x70
> [ 1.295859] ? repair_env_string+0x12/0x51
> [ 1.296215] ? parse_args+0x325/0x470
> [ 1.296532] ? __usermodehelper_set_disable_depth+0x3e/0x50
> [ 1.297006] kernel_init_freeable+0xfb/0x19a
> [ 1.297378] ? do_early_param+0x7a/0x7a
> [ 1.297708] ? rest_init+0x130/0x130
> [ 1.298030] kernel_init+0xb/0x100
> [ 1.298342] ? schedule_tail+0xc/0x60
> [ 1.298668] ? rest_init+0x130/0x130
> [ 1.298987] ret_from_fork+0x21/0x2c
> [ 1.299379] ---[ end trace e98f47d52e9cf213 ]---
> [ 1.299887] rtc-test rtc-test.0: rtc core: registered test as rtc1
>
> # HH:MM RESULT GOOD BAD GOOD_BUT_DIRTY DIRTY_NOT_BAD
> git bisect start 472b8db0e353bce9af369f566db55ab626922906 4495c08e84729385774601b5146d51d9e5849f81 --
> git bisect good 83f311c4f0a8a406485c034038d1eebb61467e06 # 10:15 G 11 0 11 11 Merge 'pm/linux-next' into devel-catchup-201703170914
> git bisect good dba0cafd19396fe23ef3688ce9f18e9a6cf12d11 # 10:28 G 11 0 11 11 Merge 'linux-review/Michael-Davidson/crypto-x86-aesni-fix-token-pasting-for-clang/20170317-082713' into devel-catchup-201703170914
> git bisect bad 533e610f1350246901b978d58268816bbbedee83 # 10:42 B 0 11 22 0 Merge 'linux-review/John-Keeping/Bluetooth-hci_bcm-Fix-clock-un-prepare/20170317-081003' into devel-catchup-201703170914
> git bisect bad a44dae33e154bb3727f7758ffe858a69c42e8ecb # 10:57 B 0 11 22 0 Merge 'char-misc/char-misc-testing' into devel-catchup-201703170914
> git bisect good def32a359b666d8d577e4c5884e0918f7ff5ba2e # 11:09 G 11 0 11 11 docs: Update VME documentation to include kerneldoc comments
> git bisect good f51de2acbb7facde8fb855c73fb9edd60cf3055e # 11:20 G 11 0 11 11 platform/chrome: cros_ec_dev - utilize new cdev_device_add helper function
> git bisect bad 4cd8adb100107dc44e63615040ca2bde43de6167 # 11:29 B 0 11 32 10 rtc: utilize new cdev_device_add helper function
> git bisect good dafa63cd90cd13262cb995a27c3c79eb3fda4655 # 11:49 G 11 0 11 11 iio:core: utilize new cdev_device_add helper function
> git bisect good cb7e71b95d29c72d1f8a2a2a0a34328bde10c3d8 # 11:56 G 11 0 11 22 mtd: utilize new cdev_device_add helper function
> git bisect good c65bbfc122b7229dacfb0e9cb208857a48eab87b # 12:02 G 11 0 11 22 rapidio: utilize new cdev_device_add helper function
> # first bad commit: [4cd8adb100107dc44e63615040ca2bde43de6167] rtc: utilize new cdev_device_add helper function
> git bisect good c65bbfc122b7229dacfb0e9cb208857a48eab87b # 12:05 G 33 0 33 55 rapidio: utilize new cdev_device_add helper function
> # extra tests with CONFIG_DEBUG_INFO_REDUCED
> git bisect bad 4cd8adb100107dc44e63615040ca2bde43de6167 # 12:16 B 0 7 18 0 rtc: utilize new cdev_device_add helper function
> # extra tests on HEAD of linux-devel/devel-catchup-201703170914
> git bisect bad 472b8db0e353bce9af369f566db55ab626922906 # 12:16 B 0 33 47 0 0day head guard for 'devel-catchup-201703170914'
> # extra tests on tree/branch char-misc/char-misc-testing
> git bisect bad 64d77f61c0c2fa6b1aa4820261943fc136a1b31e # 12:26 B 0 7 29 11 auxdisplay: Add HD44780 Character LCD support
> # extra tests with first bad commit reverted
> git bisect good 44b1351793f770c1c1f10b827a70605b996a4f73 # 12:57 G 11 0 11 11 Revert "rtc: utilize new cdev_device_add helper function"
>
> ---
> 0-DAY kernel test infrastructure Open Source Technology Center
> https://lists.01.org/pipermail/lkp Intel Corporation
>
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