linux-kernel - Re: [PATCH bpf-next 0/4] Make inode storage available to tracing prog

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Message-ID: <d3e82f51-d381-4aaf-a6aa-917d5ec08150@schaufler-ca.com>
Date: Tue, 12 Nov 2024 10:09:10 -0800
From: Casey Schaufler <casey@...aufler-ca.com>
To: Song Liu <song@...nel.org>, bpf@...r.kernel.org,
 linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-security-module@...r.kernel.org
Cc: kernel-team@...a.com, andrii@...nel.org, eddyz87@...il.com,
 ast@...nel.org, daniel@...earbox.net, martin.lau@...ux.dev,
 viro@...iv.linux.org.uk, brauner@...nel.org, jack@...e.cz,
 kpsingh@...nel.org, mattbobrowski@...gle.com, amir73il@...il.com,
 repnop@...gle.com, jlayton@...nel.org, josef@...icpanda.com,
 mic@...ikod.net, gnoack@...gle.com, Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH bpf-next 0/4] Make inode storage available to tracing prog

On 11/12/2024 12:25 AM, Song Liu wrote:
> bpf inode local storage can be useful beyond LSM programs. For example,
> bcc/libbpf-tools file* can use inode local storage to simplify the logic.
> This set makes inode local storage available to tracing program.

Mixing the storage and scope of LSM data and tracing data leaves all sorts
of opportunities for abuse. Add inode data for tracing if you can get the
patch accepted, but do not move the LSM data out of i_security. Moving
the LSM data would break the integrity (such that there is) of the LSM
model.

>
> 1/4 is missing change for bpf task local storage. 2/4 move inode local
> storage from security blob to inode.
>
> Similar to task local storage in tracing program, it is necessary to add
> recursion prevention logic for inode local storage. Patch 3/4 adds such
> logic, and 4/4 add a test for the recursion prevention logic.
>
> Song Liu (4):
>   bpf: lsm: Remove hook to bpf_task_storage_free
>   bpf: Make bpf inode storage available to tracing program
>   bpf: Add recursion prevention logic for inode storage
>   selftest/bpf: Test inode local storage recursion prevention
>
>  fs/inode.c                                    |   1 +
>  include/linux/bpf.h                           |   9 +
>  include/linux/bpf_lsm.h                       |  29 ---
>  include/linux/fs.h                            |   4 +
>  kernel/bpf/Makefile                           |   3 +-
>  kernel/bpf/bpf_inode_storage.c                | 185 +++++++++++++-----
>  kernel/bpf/bpf_lsm.c                          |   4 -
>  kernel/trace/bpf_trace.c                      |   8 +
>  security/bpf/hooks.c                          |   7 -
>  tools/testing/selftests/bpf/DENYLIST.s390x    |   1 +
>  .../bpf/prog_tests/inode_local_storage.c      |  72 +++++++
>  .../bpf/progs/inode_storage_recursion.c       |  90 +++++++++
>  12 files changed, 320 insertions(+), 93 deletions(-)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/inode_local_storage.c
>  create mode 100644 tools/testing/selftests/bpf/progs/inode_storage_recursion.c
>
> --
> 2.43.5
>