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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 15:24:24 -0800	[thread overview]
Message-ID: <CAHk-=wgkOGmkTu18hJQaJ4mk8hGZc16=gzGMgGGOd=uwpXsdyw@mail.gmail.com> (raw)
In-Reply-To: <202111171341.41053845C3@keescook>

On Wed, Nov 17, 2021 at 1:54 PM Kees Cook <keescook@chromium.org> wrote:
>
> The SA_IMMUTABLE change was to deal with failures seen in the seccomp
> test suite after the recent fatal signal refactoring. Mainly that a
> process that should have effectively performed do_exit() was suddenly
> visible to the tracer.

I think this basically shows that the conversion from do_exit() to
fatal_signal() was just wrong. The "do_exit()" wasn't really a signal,
and can't be treated as such.

That said, instead of reverting, maybe we can just mark the cases
where it really is about sending a synchronous signal, vs sending an
explicitly fatal signal.

It's basically the "true" condition to force_sig_info_to_task(), so
the fix might be just

  @@ -1323,7 +1323,8 @@ force_sig_info_to_task(struct kernel_siginfo
*info, struct task_struct *t, bool
        blocked = sigismember(&t->blocked, sig);
        if (blocked || ignored || sigdfl) {
                action->sa.sa_handler = SIG_DFL;
  -             action->sa.sa_flags |= SA_IMMUTABLE;
  +             if (sigdfl)
  +                     action->sa.sa_flags |= SA_IMMUTABLE;
                if (blocked) {
                        sigdelset(&t->blocked, sig);
                        recalc_sigpending_and_wake(t);

Kyle, does that fix your test-case? And Kees - yours?

               Linus

  reply	other threads:[~2021-11-17 23:24 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-17 18:47 [REGRESSION] 5.16rc1: SA_IMMUTABLE breaks debuggers 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 [this message]
2021-11-18  0:05             ` Kees Cook
2021-11-18  0:15               ` Linus Torvalds
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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