[Bug 200951] New: kernel NULL pointer dereference in update_sit_entry

[bugzilla-daemon@bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=200951

            Bug ID: 200951
           Summary: kernel NULL pointer dereference in update_sit_entry
           Product: File System
           Version: 2.5
    Kernel Version: v4.19-rc1, v4.18.2
          Hardware: ARM
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: high
          Priority: P1
         Component: f2fs
          Assignee: filesystem_f2fs@kernel-bugs.kernel.org
          Reporter: vicencb@gmail.com
        Regression: No

Created attachment 278127
  --> https://bugzilla.kernel.org/attachment.cgi?id=278127&action=edit
dmesg

Hi,
in the setup there is a SATA SSD connected to a SATA-to-USB bridge.

The disc is "Samsung SSD 850 PRO 256G" which supports TRIM.
There are four partitions:
 sda1: FAT  /boot
 sda2: F2FS /
 sda3: F2FS /home
 sda4: F2FS

The bridge is ASMT1153e which uses the "uas" driver.
There is no TRIM pass-through, so, when mounting it reports:
 mounting with "discard" option, but the device does not support discard

The USB host is USB3.0 and UASP capable. It is the one on RK3399.

Given this everything works fine, except there is no TRIM support.

In order to enable TRIM a new UDEV rule is added [1]:
 /etc/udev/rules.d/10-sata-bridge-trim.rules:
 ACTION=="add|change", ATTRS{idVendor}=="174c", ATTRS{idProduct}=="55aa",
SUBSYSTEM=="scsi_disk", ATTR{provisioning_mode}="unmap"
After reboot any F2FS write hangs forever and dmesg reports:
 Unable to handle kernel NULL pointer dereference

Also tested on a x86_64 system: works fine even with TRIM enabled.
 same disc
 same bridge
 different usb host controller
 different cpu architecture
 not root filesystem

Regards,
  Vicenç.

[1] Post #5 in https://bbs.archlinux.org/viewtopic.php?id=236280

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