Message-ID: <70dd7fa2-9a5f-9361-ebe0-bb337c523d09@alu.unizg.hr>
Date:   Wed, 17 May 2023 18:10:54 +0200
From:   Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Mirsad Goran Todorovac <mirsad.goran.todorovac@....hr>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-input@...r.kernel.org,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Jiri Kosina <jikos@...nel.org>
Subject: Re: [BUG][NEW DATA] Kmemleak, possibly hiddev_connect(), in 6.3.0+
 torvalds tree commit gfc4354c6e5c2

On 5/16/23 16:36, Greg Kroah-Hartman wrote:
> On Fri, May 12, 2023 at 11:33:31PM +0200, Mirsad Goran Todorovac wrote:
>> Hi,
>>
>> On 5/9/23 04:59, Greg Kroah-Hartman wrote:
>>> On Tue, May 09, 2023 at 01:51:35AM +0200, Mirsad Goran Todorovac wrote:
>>>>
>>>>
>>>> On 08. 05. 2023. 16:01, Greg Kroah-Hartman wrote:
>>>>> On Mon, May 08, 2023 at 08:51:55AM +0200, Greg Kroah-Hartman wrote:
>>>>>> On Mon, May 08, 2023 at 08:30:07AM +0200, Mirsad Goran Todorovac wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> There seems to be a kernel memory leak in the USB keyboard driver.
>>>>>>>
>>>>>>> The leaked memory allocs are 96 and 512 bytes.
>>>>>>>
>>>>>>> The platform is Ubuntu 22.04 LTS on a assembled AMD Ryzen 9 with X670E PG
>>>>>>> Lightning mobo,
>>>>>>> and Genius SlimStar i220 GK-080012 keyboard.
>>>>>>>
>>>>>>> (Logitech M100 HID mouse is not affected by the bug.)
>>>>>>>
>>>>>>> BIOS is:
>>>>>>>
>>>>>>>         *-firmware
>>>>>>>              description: BIOS
>>>>>>>              vendor: American Megatrends International, LLC.
>>>>>>>              physical id: 0
>>>>>>>              version: 1.21
>>>>>>>              date: 04/26/2023
>>>>>>>              size: 64KiB
>>>>>>>
>>>>>>> The kernel is 6.3.0-torvalds-<id>-13466-gfc4354c6e5c2.
>>>>>>>
>>>>>>> The keyboard is recognised as Chicony:
>>>>>>>
>>>>>>>                     *-usb
>>>>>>>                          description: Keyboard
>>>>>>>                          product: CHICONY USB Keyboard
>>>>>>>                          vendor: CHICONY
>>>>>>>                          physical id: 2
>>>>>>>                          bus info: usb@5:2
>>>>>>>                          logical name: input35
>>>>>>>                          logical name: /dev/input/event4
>>>>>>>                          logical name: input35::capslock
>>>>>>>                          logical name: input35::numlock
>>>>>>>                          logical name: input35::scrolllock
>>>>>>>                          logical name: input36
>>>>>>>                          logical name: /dev/input/event5
>>>>>>>                          logical name: input37
>>>>>>>                          logical name: /dev/input/event6
>>>>>>>                          logical name: input38
>>>>>>>                          logical name: /dev/input/event8
>>>>>>>                          version: 2.30
>>>>>>>                          capabilities: usb-2.00 usb
>>>>>>>                          configuration: driver=usbhid maxpower=100mA
>>>>>>> speed=1Mbit/s
>>>>>>>
>>>>>>> The bug is easily reproduced by unplugging the USB keyboard, waiting about a
>>>>>>> couple of seconds,
>>>>>>> and then reconnect and scan for memory leaks twice.
>>>>>>>
>>>>>>> The kmemleak log is as follows [edited privacy info]:
>>>>>>>
>>>>>>> root@...tname:/home/username# cat /sys/kernel/debug/kmemleak
>>>>>>> unreferenced object 0xffff8dd020037c00 (size 96):
>>>>>>>      comm "systemd-udevd", pid 435, jiffies 4294892550 (age 8909.356s)
>>>>>>>      hex dump (first 32 bytes):
>>>>>>>        5d 8e 4e b9 ff ff ff ff 00 00 00 00 00 00 00 00 ].N.............
>>>>>>>        00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
>>>>>>>      backtrace:
>>>>>>>        [<ffffffffb81a74be>] __kmem_cache_alloc_node+0x22e/0x2b0
>>>>>>>        [<ffffffffb8127b6e>] kmalloc_trace+0x2e/0xa0
>>>>>>>        [<ffffffffb87543d9>] class_create+0x29/0x80
>>>>>>>        [<ffffffffb8880d24>] usb_register_dev+0x1d4/0x2e0
>>>>>>
>>>>>> As the call to class_create() in this path is now gone in 6.4-rc1, can
>>>>>> you retry that release to see if this is still there or not?
>>>>>
>>>>> No, wait, it's still there, I was looking at a development branch of
>>>>> mine that isn't sent upstream yet.  And syzbot just reported the same
>>>>> thing:
>>>>> 	https://lore.kernel.org/r/00000000000058d15f05fb264013@google.com
>>>>>
>>>>> So something's wrong here, let me dig into it tomorrow when I get a
>>>>> chance...
>>>>
>>>> If this could help, here is the bisect of the bug (I could not discern what
>>>> could possibly be wrong):
>>>>
>>>> user@...t:~/linux/kernel/linux_torvalds$ git bisect log
>>>> git bisect start
>>>> # bad: [ac9a78681b921877518763ba0e89202254349d1b] Linux 6.4-rc1
>>>> git bisect bad ac9a78681b921877518763ba0e89202254349d1b
>>>> # good: [c9c3395d5e3dcc6daee66c6908354d47bf98cb0c] Linux 6.2
>>>> git bisect good c9c3395d5e3dcc6daee66c6908354d47bf98cb0c
>>>> # good: [85496c9b3bf8dbe15e2433d3a0197954d323cadc] Merge branch
>>>> 'net-remove-some-rcu_bh-cruft'
>>>> git bisect good 85496c9b3bf8dbe15e2433d3a0197954d323cadc
>>>> # good: [b68ee1c6131c540a62ecd443be89c406401df091] Merge tag 'scsi-misc' of
>>>> git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi
>>>> git bisect good b68ee1c6131c540a62ecd443be89c406401df091
>>>> # bad: [888d3c9f7f3ae44101a3fd76528d3dd6f96e9fd0] Merge tag 'sysctl-6.4-rc1'
>>>> of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux
>>>> git bisect bad 888d3c9f7f3ae44101a3fd76528d3dd6f96e9fd0
>>>> # good: [34b62f186db9614e55d021f8c58d22fc44c57911] Merge tag
>>>> 'pci-v6.4-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/pci/pci
>>>> git bisect good 34b62f186db9614e55d021f8c58d22fc44c57911
>>>> # good: [34da76dca4673ab1819830b4924bb5b436325b26] Merge tag
>>>> 'for-linus-2023042601' of
>>>> git://git.kernel.org/pub/scm/linux/kernel/git/hid/hid
>>>> git bisect good 34da76dca4673ab1819830b4924bb5b436325b26
>>>> # good: [97b2ff294381d05e59294a931c4db55276470cb5] Merge tag
>>>> 'staging-6.4-rc1' of
>>>> git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging
>>>> git bisect good 97b2ff294381d05e59294a931c4db55276470cb5
>>>> # good: [2025b2ca8004c04861903d076c67a73a0ec6dfca] mcb-lpc: Reallocate
>>>> memory region to avoid memory overlapping
>>>> git bisect good 2025b2ca8004c04861903d076c67a73a0ec6dfca
>>>> # bad: [d06f5a3f7140921ada47d49574ae6fa4de5e2a89] cdx: fix build failure due
>>>> to sysfs 'bus_type' argument needing to be const
>>>> git bisect bad d06f5a3f7140921ada47d49574ae6fa4de5e2a89
>>>> # good: [dcfbb67e48a2becfce7990386e985b9c45098ee5] driver core: class: use
>>>> lock_class_key already present in struct subsys_private
>>>> git bisect good dcfbb67e48a2becfce7990386e985b9c45098ee5
>>>> # bad: [6f14c02220c791d5c46b0f965b9340c58f3d503d] driver core: create
>>>> class_is_registered()
>>>> git bisect bad 6f14c02220c791d5c46b0f965b9340c58f3d503d
>>>> # good: [2f9e87f5a2941b259336c7ea6c5a1499ede4554a] driver core: Add a
>>>> comment to set_primary_fwnode() on nullifying
>>>> git bisect good 2f9e87f5a2941b259336c7ea6c5a1499ede4554a
>>>> # bad: [02fe26f25325b547b7a31a65deb0326c04bb5174] firmware_loader: Add debug
>>>> message with checksum for FW file
>>>> git bisect bad 02fe26f25325b547b7a31a65deb0326c04bb5174
>>>> # good: [884f8ce42ccec9d0bf11d8bf9f111e5961ca1c82] driver core: class:
>>>> implement class_get/put without the private pointer.
>>>> git bisect good 884f8ce42ccec9d0bf11d8bf9f111e5961ca1c82
>>>> # bad: [3f84aa5ec052dba960baca4ab8a352d43d47028e] base: soc: populate
>>>> machine name in soc_device_register if empty
>>>> git bisect bad 3f84aa5ec052dba960baca4ab8a352d43d47028e
>>>> # bad: [7b884b7f24b42fa25e92ed724ad82f137610afaf] driver core: class.c:
>>>> convert to only use class_to_subsys
>>>> git bisect bad 7b884b7f24b42fa25e92ed724ad82f137610afaf
>>>> # first bad commit: [7b884b7f24b42fa25e92ed724ad82f137610afaf] driver core:
>>>> class.c: convert to only use class_to_subsys
>>>> user@...t:~/linux/kernel/linux_torvalds$
>>>
>>> This helps a lot, thanks.  I got the reference counting wrong somewhere
>>> in here, I thought I tested this better, odd it shows up now...
>>>
>>> I'll try to work on it this week.
>>
>> I have figured out that the leak occurs on keyboard unplugging only, one
>> or two leaks (maybe a race condition?).
>>
>> Please NOTE that the number of leaks is now odd:
>>
>> root@...iant:/home/marvin# cat /sys/kernel/debug/kmemleak | grep comm
>>    comm "systemd-udevd", pid 330, jiffies 4294892588 (age 715.772s)
>>    comm "systemd-udevd", pid 330, jiffies 4294892588 (age 715.772s)
>>    comm "kworker/6:0", pid 54, jiffies 4294907989 (age 654.224s)
>>    comm "kworker/6:0", pid 54, jiffies 4294907989 (age 654.272s)
>>    comm "kworker/6:3", pid 3046, jiffies 4294935362 (age 544.780s)
>>    comm "kworker/6:0", pid 54, jiffies 4294964122 (age 429.740s)
>>    comm "kworker/6:0", pid 54, jiffies 4294964122 (age 429.784s)
>> root@...iant:/home/marvin#
>>
>> At one time unplugging keyboard generated only one leak, but only at one
>> time. As it requires manually unplugging keyboard, I didn't seem to find a
>> way to automate it, but it doesn't seem to require root access.
>>
>> BTW, I've seen in syzbot output that kmemleak output has debug source file
>> names and line numbers. I couldn't make that work with the dbg .deb.
>>
>> I will do some more homework, but this was a rough week.
> 
> I made up a patch based on code inspection alone, as I couldn't
> reproduce this locally at all:
> 	https://lore.kernel.org/r/2023051628-thumb-boaster-5680@gregkh
> and it seemed to pass syzbot's tests.
> 
> I've included it here below, can you test it as well?
> 
> Hm, I only tested with a USB mouse unplug/plug cycle, maybe the issue is
> a keyboard?
> 
> thanks,
> 
> greg k-h
> 
> -------------
> 
> diff --git a/drivers/base/class.c b/drivers/base/class.c
> index ac1808d1a2e8..9b44edc8416f 100644
> --- a/drivers/base/class.c
> +++ b/drivers/base/class.c
> @@ -320,6 +322,7 @@ void class_dev_iter_init(struct class_dev_iter *iter, const struct class *class,
>   		start_knode = &start->p->knode_class;
>   	klist_iter_init_node(&sp->klist_devices, &iter->ki, start_knode);
>   	iter->type = type;
> +	iter->sp = sp;
>   }
>   EXPORT_SYMBOL_GPL(class_dev_iter_init);
>   
> @@ -361,6 +364,7 @@ EXPORT_SYMBOL_GPL(class_dev_iter_next);
>   void class_dev_iter_exit(struct class_dev_iter *iter)
>   {
>   	klist_iter_exit(&iter->ki);
> +	subsys_put(iter->sp);
>   }
>   EXPORT_SYMBOL_GPL(class_dev_iter_exit);
>   
> diff --git a/include/linux/device/class.h b/include/linux/device/class.h
> index 9deeaeb457bb..abf3d3bfb6fe 100644
> --- a/include/linux/device/class.h
> +++ b/include/linux/device/class.h
> @@ -74,6 +74,7 @@ struct class {
>   struct class_dev_iter {
>   	struct klist_iter		ki;
>   	const struct device_type	*type;
> +	struct subsys_private		*sp;
>   };
>   
>   int __must_check class_register(const struct class *class);

The build with the latest 6.4-rc2 and without this patch still leaked,
the build with the same commit and this patch applied was successful:

root@...iant:/home/marvin# cat /sys/kernel/debug/kmemleak
root@...iant:/home/marvin#

Tried three times, and it is a OK.

Congratulations! This had fixed the leak.

I wonder why it didn't show in the other contexts, hardware and archs?

Best regards,
Mirsad

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