From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 57D4FC433EF for ; Wed, 24 Nov 2021 01:33:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233882AbhKXBgq (ORCPT ); Tue, 23 Nov 2021 20:36:46 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46170 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233736AbhKXBgq (ORCPT ); Tue, 23 Nov 2021 20:36:46 -0500 Received: from mail-ed1-x534.google.com (mail-ed1-x534.google.com [IPv6:2a00:1450:4864:20::534]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 23673C061574 for ; Tue, 23 Nov 2021 17:33:37 -0800 (PST) Received: by mail-ed1-x534.google.com with SMTP id y13so2742745edd.13 for ; Tue, 23 Nov 2021 17:33:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kylehuey.com; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Bdk3dunfmKliz7CIhG/Qu1R5YQt3NI9C/XigAL1L5Jw=; b=YMfucddRfd5aY00RTMNNKSFdm8h6mbG8pH9k63i4FRMqchpsj1w/+wKsBOfr/aW1tQ FqtGYWuc+26HU3VRIXIKTH2d6k1vKzWosS1saRGuZ4c85cClUqeZY6twr5JhGw2WPkIJ NBJ8pwuScNRZO9wmVojnObYTNs6cJdIcAGTBPPVtlugv8NbXO3lhJkoFnj5h4ZNYCMhS 2qv95j+4Q00QOyUllvFQPNtfmEyeNYEZedDzWOSfxzS1w2Yk7EYgPvu9ISYXYZgNaf+H hkm0fRP8P+GIQ5cqJdZJhryHQVFx6ZucsK2RJW3TgVVgIJ8arccYa/CR7jWyeLZsGM94 W4cg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Bdk3dunfmKliz7CIhG/Qu1R5YQt3NI9C/XigAL1L5Jw=; b=AlX4joxT3B/dYD34SefY/D3kZ179/nq5cMIFxszBYqV+TCS+CPZSOIAuWWW73wcQeC EwCEvCC/Dv/SC3jWxDyzo02F2UoDJt7U7YS3/IQUvRYWfAjEc55AM/6kIt3Y0vH8rTQA 36odTUDuHg4Bei1mO9fUpFFDLCTocJDJFwkKbsGpt6Q6nUSONFwaRyz8wSFKzn52Z1pu 7BrwQ9wlCXahweFkZ3N+TSWyk31uhc6C6TZp8rjjEzsYgCwtASleFQieI1hgfGfZxKVy IqqcqLAjardpMZ45M0/zaXJgHWcnhR98EN/+0rbR+hwU+ust43jBiLi/r15m6vyud2Zn Yb+g== X-Gm-Message-State: AOAM530HeyDpsdQ6GZ4ySgVWViy96EaTuPkFR278lPfTnOZODmQ2cN+/ 1kLlop3W1uAt6QKyIebYTQovttKuNM/kx9+OpGIHCQ== X-Google-Smtp-Source: ABdhPJyzt2nLXv21cUImChEwlWHlb4vk5j+Z04hlfyxmWQMt3NF+7BV+76JBiHbFc2XA/UeDkMGubECfnTnBI+fixew= X-Received: by 2002:a17:907:6e1a:: with SMTP id sd26mr13885184ejc.529.1637717615604; Tue, 23 Nov 2021 17:33:35 -0800 (PST) MIME-Version: 1.0 References: <163758427225348@kroah.com> In-Reply-To: <163758427225348@kroah.com> From: Kyle Huey Date: Tue, 23 Nov 2021 17:33:19 -0800 Message-ID: Subject: Re: FAILED: patch "[PATCH] signal: Don't always set SA_IMMUTABLE for forced signals" failed to apply to 5.15-stable tree To: gregkh@linuxfoundation.org, "Robert O'Callahan" Cc: "Eric W. Biederman" , Kees Cook , Kyle Huey , Oliver Sang , Linus Torvalds , stable@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Mon, Nov 22, 2021 at 4:31 AM wrote: > > > The patch below does not apply to the 5.15-stable tree. > If someone wants it applied there, or to any other stable or longterm > tree, then please email the backport, including the original git commit > id to . > > thanks, > > greg k-h > > ------------------ original commit in Linus's tree ------------------ > > From e349d945fac76bddc78ae1cb92a0145b427a87ce Mon Sep 17 00:00:00 2001 > From: "Eric W. Biederman" > Date: Thu, 18 Nov 2021 11:11:13 -0600 > Subject: [PATCH] signal: Don't always set SA_IMMUTABLE for forced signals > > Recently to prevent issues with SECCOMP_RET_KILL and similar signals > being changed before they are delivered SA_IMMUTABLE was added. > > Unfortunately this broke debuggers[1][2] which reasonably expect to be > able to trap synchronous SIGTRAP and SIGSEGV even when the target > process is not configured to handle those signals. > > Update force_sig_to_task to support both the case when we can allow > the debugger to intercept and possibly ignore the signal and the case > when it is not safe to let userspace know about the signal until the > process has exited. > > Suggested-by: Linus Torvalds > Reported-by: Kyle Huey > Reported-by: kernel test robot > Cc: stable@vger.kernel.org > [1] https://lkml.kernel.org/r/CAP045AoMY4xf8aC_4QU_-j7obuEPYgTcnQQP3Yxk=2X90jtpjw@mail.gmail.com > [2] https://lkml.kernel.org/r/20211117150258.GB5403@xsang-OptiPlex-9020 > Fixes: 00b06da29cf9 ("signal: Add SA_IMMUTABLE to ensure forced siganls do not get changed") > Link: https://lkml.kernel.org/r/877dd5qfw5.fsf_-_@email.froward.int.ebiederm.org > Reviewed-by: Kees Cook > Tested-by: Kees Cook > Tested-by: Kyle Huey > Signed-off-by: "Eric W. Biederman" > > diff --git a/kernel/signal.c b/kernel/signal.c > index 7c4b7ae714d4..7815e1bbeddc 100644 > --- a/kernel/signal.c > +++ b/kernel/signal.c > @@ -1298,6 +1298,12 @@ int do_send_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *p > return ret; > } > > +enum sig_handler { > + HANDLER_CURRENT, /* If reachable use the current handler */ > + HANDLER_SIG_DFL, /* Always use SIG_DFL handler semantics */ > + HANDLER_EXIT, /* Only visible as the process exit code */ > +}; > + > /* > * Force a signal that the process can't ignore: if necessary > * we unblock the signal and change any SIG_IGN to SIG_DFL. > @@ -1310,7 +1316,8 @@ int do_send_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *p > * that is why we also clear SIGNAL_UNKILLABLE. > */ > static int > -force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t, bool sigdfl) > +force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t, > + enum sig_handler handler) > { > unsigned long int flags; > int ret, blocked, ignored; > @@ -1321,9 +1328,10 @@ force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t, bool > action = &t->sighand->action[sig-1]; > ignored = action->sa.sa_handler == SIG_IGN; > blocked = sigismember(&t->blocked, sig); > - if (blocked || ignored || sigdfl) { > + if (blocked || ignored || (handler != HANDLER_CURRENT)) { > action->sa.sa_handler = SIG_DFL; > - action->sa.sa_flags |= SA_IMMUTABLE; > + if (handler == HANDLER_EXIT) > + action->sa.sa_flags |= SA_IMMUTABLE; > if (blocked) { > sigdelset(&t->blocked, sig); > recalc_sigpending_and_wake(t); > @@ -1343,7 +1351,7 @@ force_sig_info_to_task(struct kernel_siginfo *info, struct task_struct *t, bool > > int force_sig_info(struct kernel_siginfo *info) > { > - return force_sig_info_to_task(info, current, false); > + return force_sig_info_to_task(info, current, HANDLER_CURRENT); > } > > /* > @@ -1660,7 +1668,7 @@ void force_fatal_sig(int sig) > info.si_code = SI_KERNEL; > info.si_pid = 0; > info.si_uid = 0; > - force_sig_info_to_task(&info, current, true); > + force_sig_info_to_task(&info, current, HANDLER_SIG_DFL); > } > > /* > @@ -1693,7 +1701,7 @@ int force_sig_fault_to_task(int sig, int code, void __user *addr > info.si_flags = flags; > info.si_isr = isr; > #endif > - return force_sig_info_to_task(&info, t, false); > + return force_sig_info_to_task(&info, t, HANDLER_CURRENT); > } > > int force_sig_fault(int sig, int code, void __user *addr > @@ -1813,7 +1821,8 @@ int force_sig_seccomp(int syscall, int reason, bool force_coredump) > info.si_errno = reason; > info.si_arch = syscall_get_arch(current); > info.si_syscall = syscall; > - return force_sig_info_to_task(&info, current, force_coredump); > + return force_sig_info_to_task(&info, current, > + force_coredump ? HANDLER_EXIT : HANDLER_CURRENT); > } > > /* For the crazy architectures that include trap information in > Since this is taken care of now, AFAICT, I do have one additional question. I reported the regression to LKML a day or so before 5.15.3 was cut. What should I have noticed to see that the regressing changeset was going to 5.15 and where should I have said "hey please don't ship this on 5.15 yet"? I'd like to know what to do next time :) - Kyle