linux-kernel - Re: [GIT PULL] lsm/lsm-pr-20240105

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Message-ID: <CAHk-=winAVoX=u+uX1Cdf0ekmFHETumRr60rvC_z6jbno0ApPg@mail.gmail.com>
Date: Wed, 10 Jan 2024 12:22:10 -0800
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Paul Moore <paul@...l-moore.com>
Cc: linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL] lsm/lsm-pr-20240105

On Wed, 10 Jan 2024 at 11:54, Paul Moore <paul@...l-moore.com> wrote:
>
> Thanks for pulling the changes, I'm sorry the syscall table entries
> for the LSM syscalls were not how you want to see them, but I'm more
> than a little confused as to what exactly we did wrong here.

Look at commit 5f42375904b0 ("LSM: wireup Linux Security Module
syscalls") and notice for example this:

  --- a/arch/x86/entry/syscalls/syscall_64.tbl
  +++ b/arch/x86/entry/syscalls/syscall_64.tbl
  @@ -378,6 +378,9 @@
   454    common  futex_wake              sys_futex_wake
   455    common  futex_wait              sys_futex_wait
   456    common  futex_requeue           sys_futex_requeue
  +457    common  lsm_get_self_attr       sys_lsm_get_self_attr
  +458    common  lsm_set_self_attr       sys_lsm_set_self_attr
  +459    common  lsm_list_modules        sys_lsm_list_modules

Ok, fine - you added your new system calls to the end of the table.
Sure, I ended up having to fix them up because the "end of the table"
was different by the time I merged your tree, but that wasn't the
problem.

The problem is here - in the same commit:

  --- a/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl
  +++ b/tools/perf/arch/x86/entry/syscalls/syscall_64.tbl
  @@ -375,6 +375,9 @@
   451    common  cachestat               sys_cachestat
   452    common  fchmodat2               sys_fchmodat2
   453    64      map_shadow_stack        sys_map_shadow_stack
  +454    common  lsm_get_self_attr       sys_lsm_get_self_attr
  +455    common  lsm_set_self_attr       sys_lsm_set_self_attr
  +456    common  lsm_list_modules        sys_lsm_list_modules

note how you updated the tools copy WITH THE WRONG NUMBERS!

You just added them at the end of the table again, and just
incremented the numbers, but that was complete nonsense, because the
numbers didn't actually match the real system call numbers, because
that tools table hadn't been updated for new system calls - because it
hadn't needed them.

Yeah, our tooling header duplication is annoying, but the old
situation where the tooling just used various kernel headers directly
and would randomly break when kernel changes were made was even worse.

End result: avoid touching the tooling headers - and if you have to,
you need to *think* about it.

           Linus