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

From: Mirsad Goran Todorovac
Date: Fri May 12 2023 - 15:08:12 EST

Hi, Greg,

On 09. 05. 2023. 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@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 ................
  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@xxxxxxxxxx

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@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
'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@host:~/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.

thanks,

greg k-h

Not at all!

I hope you had better luck because this part of code still looks to me like hieroglyphs.

Linux kernel rose to 10.9M lines, and it would take me thirty years to
just read it once, 1000 lines a day ... 6.7M lines are "just drivers".

# find . -name '*.c' -o -name '*.h' -print0 | wc --files0-from -
10913623 35587483 631377958 total
# find drivers -name '*.c' -o -name '*.h' -print0 | wc --files0-from -
6705084 19985060 495162001 total

Best regards,
Mirsad