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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8DD1CC433FE for ; Mon, 15 Nov 2021 17:27:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 70577632ED for ; Mon, 15 Nov 2021 17:27:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237513AbhKOR3v (ORCPT ); Mon, 15 Nov 2021 12:29:51 -0500 Received: from mail.kernel.org ([198.145.29.99]:46616 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236852AbhKORO4 (ORCPT ); Mon, 15 Nov 2021 12:14:56 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 6064363250; Mon, 15 Nov 2021 17:11:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1636996292; bh=XunzDaa8N7lpnorS4BtkwbO051ejfol5eKt5qaAtSx0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=v3g/0buEEtnDaSCSbcC7c1s84kw+KdLBpFWaiLT1vCZKIbKDuUlYfTUXlj1vrDW8K vctrGhR0j4qNCXSvkrNo8Rf+2hKL9Lfj80nlRLHuIk712ahqzUkG4hAV+78P7EI7oc fpBCUXT/OiN69BSJ8/+Zcyr6j2ytStoxJTsGYu34= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Kees Cook , "Eric W. Biederman" Subject: [PATCH 5.4 086/355] signal: Remove the bogus sigkill_pending in ptrace_stop Date: Mon, 15 Nov 2021 18:00:10 +0100 Message-Id: <20211115165316.585318865@linuxfoundation.org> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20211115165313.549179499@linuxfoundation.org> References: <20211115165313.549179499@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Eric W. Biederman commit 7d613f9f72ec8f90ddefcae038fdae5adb8404b3 upstream. The existence of sigkill_pending is a little silly as it is functionally a duplicate of fatal_signal_pending that is used in exactly one place. Checking for pending fatal signals and returning early in ptrace_stop is actively harmful. It casues the ptrace_stop called by ptrace_signal to return early before setting current->exit_code. Later when ptrace_signal reads the signal number from current->exit_code is undefined, making it unpredictable what will happen. Instead rely on the fact that schedule will not sleep if there is a pending signal that can awaken a task. Removing the explict sigkill_pending test fixes fixes ptrace_signal when ptrace_stop does not stop because current->exit_code is always set to to signr. Cc: stable@vger.kernel.org Fixes: 3d749b9e676b ("ptrace: simplify ptrace_stop()->sigkill_pending() path") Fixes: 1a669c2f16d4 ("Add arch_ptrace_stop") Link: https://lkml.kernel.org/r/87pmsyx29t.fsf@disp2133 Reviewed-by: Kees Cook Signed-off-by: "Eric W. Biederman" Signed-off-by: Greg Kroah-Hartman --- kernel/signal.c | 18 ++++-------------- 1 file changed, 4 insertions(+), 14 deletions(-) --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2101,15 +2101,6 @@ static inline bool may_ptrace_stop(void) return true; } -/* - * Return non-zero if there is a SIGKILL that should be waking us up. - * Called with the siglock held. - */ -static bool sigkill_pending(struct task_struct *tsk) -{ - return sigismember(&tsk->pending.signal, SIGKILL) || - sigismember(&tsk->signal->shared_pending.signal, SIGKILL); -} /* * This must be called with current->sighand->siglock held. @@ -2136,17 +2127,16 @@ static void ptrace_stop(int exit_code, i * calling arch_ptrace_stop, so we must release it now. * To preserve proper semantics, we must do this before * any signal bookkeeping like checking group_stop_count. - * Meanwhile, a SIGKILL could come in before we retake the - * siglock. That must prevent us from sleeping in TASK_TRACED. - * So after regaining the lock, we must check for SIGKILL. */ spin_unlock_irq(¤t->sighand->siglock); arch_ptrace_stop(exit_code, info); spin_lock_irq(¤t->sighand->siglock); - if (sigkill_pending(current)) - return; } + /* + * schedule() will not sleep if there is a pending signal that + * can awaken the task. + */ set_special_state(TASK_TRACED); /*