Re: [BUG][NEW DATA] Kmemleak, possibly hiddev_connect(), in 6.3.0+ torvalds tree commit gfc4354c6e5c2

From: Mirsad Goran Todorovac
Date: Fri May 12 2023 - 17:33:51 EST


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:

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:

          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:

                      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

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@hostname:/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 ................
    [<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

So something's wrong here, let me dig into it tomorrow when I get a

If this could help, here is the bisect of the bug (I could not discern what
could possibly be wrong):

user@host:~/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
git bisect good 85496c9b3bf8dbe15e2433d3a0197954d323cadc
# good: [b68ee1c6131c540a62ecd443be89c406401df091] Merge tag 'scsi-misc' of
git bisect good b68ee1c6131c540a62ecd443be89c406401df091
# bad: [888d3c9f7f3ae44101a3fd76528d3dd6f96e9fd0] Merge tag 'sysctl-6.4-rc1'
of git://
git bisect bad 888d3c9f7f3ae44101a3fd76528d3dd6f96e9fd0
# good: [34b62f186db9614e55d021f8c58d22fc44c57911] Merge tag
'pci-v6.4-changes' of git://
git bisect good 34b62f186db9614e55d021f8c58d22fc44c57911
# good: [34da76dca4673ab1819830b4924bb5b436325b26] Merge tag
'for-linus-2023042601' of
git bisect good 34da76dca4673ab1819830b4924bb5b436325b26
# good: [97b2ff294381d05e59294a931c4db55276470cb5] Merge tag
'staging-6.4-rc1' of
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
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

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@defiant:/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)

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.

Best regards,