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 X-Spam-Level: X-Spam-Status: No, score=-20.4 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 209DCC43457 for ; Fri, 16 Oct 2020 02:40:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C069120897 for ; Fri, 16 Oct 2020 02:40:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="MddfLAWG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404239AbgJPCko (ORCPT ); Thu, 15 Oct 2020 22:40:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57584 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404228AbgJPCkm (ORCPT ); Thu, 15 Oct 2020 22:40:42 -0400 Received: from mail-wr1-x442.google.com (mail-wr1-x442.google.com [IPv6:2a00:1450:4864:20::442]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3B012C0613D3 for ; Thu, 15 Oct 2020 19:40:42 -0700 (PDT) Received: by mail-wr1-x442.google.com with SMTP id g12so908635wrp.10 for ; Thu, 15 Oct 2020 19:40:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=IcagjNj/dK1Y8RczpuQCkX5yBuEwqqFKdmDjpHwB/uo=; b=MddfLAWGyYBRfNuN1ok8b6DU3DiyooyjcqJoJfOhV+LJKWza09r9Go8ofj1LC/QisZ RX1U7FiWILjd8tJ4OPgtOUEDISb8w3/bkgvVAJMxqUZUHmQ+HhuSYJFp/Ralp9ECoDZq SMtrG+132hhR9UTmdkq2zSCiGcjHv1krB4OeKFj1QSfxQBK595gy4ZNGwhxkNu3BZxOK bn81x1r9B6DOkbjCVmkPpnJ/P0Hiju8Dg99yreeh5ABC2m7yGbRjs7seprwLuOdcEt5s My5XZ+XMcAOZGWsPD45667KU2tZIhqcxBWzE2Ng//a54J+Tl1nGWSutjgrXIQcYbJuar Ctig== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=IcagjNj/dK1Y8RczpuQCkX5yBuEwqqFKdmDjpHwB/uo=; b=pKzbw9hPeyYDTrV1xgRtstAxLPvl7l0MkMKIpL3ulQoYwd7WIYVoBsLzaUfmDfmpOX X7HhDxvxqt+9jfgJR1MS6sDo22SRJolbs9neCnbyx9fPi4w4xYzvF2qN6Ky3lDSh51Q+ dnsnWh3tsPJdmsHAYB7T3UWT4JpE9MBbGRsyVJZ09K8nzYOoN5KwDw0CL1yfqVsX3N+1 +K5hnBf0y2mz6U7OKukBus7LKznG0cOInnwiy238npO4wBjJTOyhzPaL0B0+KyZ1PJwR PEFgFJ3YDnhf63ewg5AIYOMfBW3GcSvjyJM8aIZBygoIRerbLO73Qx/oFiFBQN2k5KND LMZw== X-Gm-Message-State: AOAM5324BdRWeqNrfFg8I7CqIATMEDkpQcs5XgbY3mnBttQsOtPI62Tf AJXRFlHg9UM3Bc7QTODa/M6n4A== X-Google-Smtp-Source: ABdhPJximA8TmzkmMulZ0xLdHIxKgoI2ci4m2SYAs/YeDnDT1bJXj91PiKhT9FEUOj80FiKoKk0j4Q== X-Received: by 2002:adf:f74e:: with SMTP id z14mr1179844wrp.312.1602816040727; Thu, 15 Oct 2020 19:40:40 -0700 (PDT) Received: from localhost ([2a02:168:96c5:1:55ed:514f:6ad7:5bcc]) by smtp.gmail.com with ESMTPSA id z5sm1511651wrw.37.2020.10.15.19.40.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Oct 2020 19:40:40 -0700 (PDT) From: Jann Horn To: Andrew Morton , linux-mm@kvack.org, Eric Biederman , Oleg Nesterov Cc: linux-kernel@vger.kernel.org, Will Deacon , Kees Cook , Ingo Molnar Subject: [RFC PATCH 5/6] ptrace: Use mm_ref() for ->exit_mm Date: Fri, 16 Oct 2020 04:40:18 +0200 Message-Id: <20201016024019.1882062-6-jannh@google.com> X-Mailer: git-send-email 2.29.0.rc1.297.gfa9743e501-goog In-Reply-To: <20201016024019.1882062-1-jannh@google.com> References: <20201016024019.1882062-1-jannh@google.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We only use ->exit_mm to look up dumpability and the ->user_mm; we don't need to keep the PGD alive for this. mmgrab() is also inconvenient here, because it means that we need to use mmdrop_async() when dropping the reference to the mm from an RCU callback. Use mm_ref() instead of mmgrab() to make things neater. Signed-off-by: Jann Horn --- kernel/exit.c | 2 +- kernel/fork.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/exit.c b/kernel/exit.c index 97253ef33486..03ba6d13ef1e 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -476,7 +476,7 @@ static void exit_mm(void) /* more a memory barrier than a real lock */ task_lock(current); current->mm = NULL; - mmgrab(mm); /* for current->exit_mm */ + mm_ref(mm); /* for current->exit_mm */ current->exit_mm = mm; mmap_read_unlock(mm); enter_lazy_tlb(mm, current); diff --git a/kernel/fork.c b/kernel/fork.c index 59c119b03351..4383bf055b40 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -720,7 +720,7 @@ void free_task(struct task_struct *tsk) if (tsk->flags & PF_KTHREAD) free_kthread_struct(tsk); if (tsk->exit_mm) - mmdrop_async(tsk->exit_mm); + mm_unref(tsk->exit_mm); free_task_struct(tsk); } EXPORT_SYMBOL(free_task); -- 2.29.0.rc1.297.gfa9743e501-goog