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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Kees Cook <keescook@chromium.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
	Kyle Huey <me@kylehuey.com>,
	Andrea Righi <andrea.righi@canonical.com>,
	Shuah Khan <shuah@kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Andy Lutomirski <luto@amacapital.net>,
	Will Drewry <wad@chromium.org>,
	"open list:KERNEL SELFTEST FRAMEWORK" 
	<linux-kselftest@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
	open list <linux-kernel@vger.kernel.org>,
	linux-hardening@vger.kernel.org,
	"Robert O'Callahan" <rocallahan@gmail.com>
Subject: Re: [REGRESSION] 5.16rc1: SA_IMMUTABLE breaks debuggers
Date: Wed, 17 Nov 2021 16:15:21 -0800	[thread overview]
Message-ID: <CAHk-=wjsyDcohs=i0XGu0GRb6AkXUNyWCE_f6JMy0RY9wdXUXg@mail.gmail.com> (raw)
In-Reply-To: <202111171603.34F36D0E01@keescook>

On Wed, Nov 17, 2021 at 4:05 PM Kees Cook <keescook@chromium.org> wrote:
>
> (nit: should the "sigdfl" argument be renamed "immutable" for clarity
> in this function?)

I don't think that would necessarily clarify anything. Neither
"sigdfl" nor "immutable" makes at least me go "Ahh, that explains
things".

Both "sigdfl" and "immutable" are about random internal implementation
choices ("force SIGDFL" and "set SA_IMMUTABLE" respectively).

I think naming things by random internal implementation things is
questionable in general, but it's particularly questionable when they
aren't even some really fundamental thing.

I think you generally want to name things not by how they do
something, but by *WHAT* they do.

So I think the proper name for it would be "fatal" or something like
that. It's basically saying "This signal is fatal, even if you have a
handler for it or not". That "set it to SIGDFL" just happens to be how
we made it fatal.

And then we should perhaps also make such a signal uncatchable by the
debugger (rather than just "debugger cannot undo or modify it" like
the SA_IMMUTABLE bit does).

Anybody want to take on that renaming / uncatchable part? Please take
my (now at least tested by Kees) patch and make it your own.

              Linus

  reply	other threads:[~2021-11-18  0:15 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-17 18:47 Kyle Huey
2021-11-17 18:51 ` Kees Cook
2021-11-17 19:05   ` Kyle Huey
2021-11-17 19:09     ` Kyle Huey
2021-11-17 21:04       ` Eric W. Biederman
2021-11-17 21:54         ` Kees Cook
2021-11-17 23:24           ` Linus Torvalds
2021-11-18  0:05             ` Kees Cook
2021-11-18  0:15               ` Linus Torvalds [this message]
2021-11-18  0:37             ` Kyle Huey
2021-11-18  1:11               ` Linus Torvalds
2021-11-18  1:20                 ` Kyle Huey
2021-11-18  1:32                   ` Kees Cook
2021-11-18 16:10                     ` Eric W. Biederman
2021-11-19 16:07                       ` Kyle Huey
2021-11-19 16:35                         ` Kees Cook
2021-11-19 16:58                           ` Kyle Huey
2021-11-18 21:58                     ` [PATCH 0/2] SA_IMMUTABLE fixes Eric W. Biederman
2021-11-18 22:04                       ` [PATCH 1/2] signal: Don't always set SA_IMMUTABLE for forced signals Eric W. Biederman
2021-11-18 23:52                         ` Kees Cook
2021-11-18 23:54                         ` Kees Cook
2021-11-19 15:08                           ` Eric W. Biederman
2021-11-19  1:13                         ` Kyle Huey
2021-11-19 15:03                           ` Eric W. Biederman
2021-11-18 22:05                       ` [PATCH 2/2] signal: Replace force_fatal_sig with force_exit_sig when in doubt Eric W. Biederman
2021-11-18 23:53                         ` Kees Cook
2021-11-19  1:12                       ` [PATCH 0/2] SA_IMMUTABLE fixes Kyle Huey
2021-11-19 15:41                         ` [GIT PULL] SA_IMMUTABLE fixes for v5.16-rc2 Eric W. Biederman
2021-11-19 19:46                           ` pr-tracker-bot
2021-11-17 22:29         ` [REGRESSION] 5.16rc1: SA_IMMUTABLE breaks debuggers Kyle Huey
2021-11-18  5:43 ` Thorsten Leemhuis
2021-11-20  6:13   ` Thorsten Leemhuis

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