[Bug] possible deadlock in vfs_rmdir in Linux kernel v6.12

[Luka <luka.2016.cs@gmail.com>]

Dear Kernel Maintainers,

I am writing to report a potential vulnerability identified in the
upstream Linux Kernel version v6.12, corresponding to the following
commit in the mainline repository:

Git Commit:  adc218676eef25575469234709c2d87185ca223a (tag: v6.12)

This issue was discovered during the testing of the Android 16 AOSP
kernel, which is based on Linux kernel version 6.12, specifically from
the AOSP kernel branch:

AOSP kernel branch: android16-6.12
Manifest path: kernel/common.git
Source URL:  https://android.googlesource.com/kernel/common/+/refs/heads/android16-6.12

Although this kernel branch is used in Android 16 development, its
base is aligned with the upstream Linux v6.12 release. I observed this
issue while conducting stability and fuzzing tests on the Android 16
platform and identified that the root cause lies in the upstream
codebase.


Bug Location: vfs_rmdir+0x118/0x488 fs/namei.c:4329

Bug Report: https://hastebin.com/share/vobatolola.bash

Entire Log: https://hastebin.com/share/efajodumuh.perl


Thank you very much for your time and attention. I sincerely apologize
that I am currently unable to provide a reproducer for this issue.
However, I am actively working on reproducing the problem, and I will
make sure to share any findings or reproducing steps with you as soon
as they are available.

I greatly appreciate your efforts in maintaining the Linux kernel and
your attention to this matter.

Best regards,
Luka