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=-2.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 DFA7AC43603 for ; Tue, 17 Dec 2019 13:39:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AF8FE206B7 for ; Tue, 17 Dec 2019 13:39:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="C3MO13fg" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728470AbfLQNjF (ORCPT ); Tue, 17 Dec 2019 08:39:05 -0500 Received: from mail-pj1-f66.google.com ([209.85.216.66]:36818 "EHLO mail-pj1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726164AbfLQNjF (ORCPT ); Tue, 17 Dec 2019 08:39:05 -0500 Received: by mail-pj1-f66.google.com with SMTP id n96so4612850pjc.3 for ; Tue, 17 Dec 2019 05:39:04 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-transfer-encoding:content-language; bh=gQB/ChgAWQAu7G8p8psPdHNZa+37XvUfN0MT2cx9AJw=; b=C3MO13fg4kp2wcV2fZP/7YYtFp8l8UWm0p9xA1Bos9vl/PuNhwOyCdzuykCwsdhhhJ mZVLQ25wX6+IU13xBaSHVYujN1KaGKj+EwXi5VXyWAyk/Sn8ZxDT5eh614WxXIWBfFr/ W+KWUrHuAh6SV7u1dycxa1nAXZe19I+H/iUqhSOaey/IWw2YAmXFcx/jG4z+exbMNm5S IdOxzZtEZb+d0bj47FE+4xVVHlH8AWZGfYeMU1ukivBeOTNLCyYAxorH8BuDT+BYwoEG +rjAKa5iqifn4uqo7wVcN6hfF2mznO2cj6skjB9x5kbOJqADfajGEBSUBSnzodCdeCgv LUqw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=gQB/ChgAWQAu7G8p8psPdHNZa+37XvUfN0MT2cx9AJw=; b=BEGxPQoMaMt7tVBYkexUBanlTNdYee8YcKZrT7pYWnOX+Ls5/r4K0IuJAxDziTzZGA m+vCP7TXDt3XnPBtn1gE/4MI45hoMUzExbRBLCQrSOeGu421SuTlLu5LTuwzMwhA/iXp rW8HAfZZ5gKChp3ykEyPymUkMfM+XC5MLCFax6JfoHvllbE1TSXnu/KkzRrb/jPBD0F5 k96BVZ0i7NqGjUhTHlfQdhesAOuVHf0fpAGf4hyJes3qDl7w6s5sj2flH4PHKZXvUNRv JtU4ZYzCTvxT36Jw63AUMTfo8Li0LqEFIrYagKfHiZhQoKDDfDxcTMUihv4k9Qzzlc8r 7GEw== X-Gm-Message-State: APjAAAXv0VYLYIHBydmQaoPCvv1psu2yXzEFb+9B1RcoceCNYFKP5KoW 8+vV+jEJ/J0BRmd4Oa6YKrNB/gj+H50= X-Google-Smtp-Source: APXvYqxF6nDsn2S+SZ2JsyXauAy4vKm2CsBjNVueBRjJRtIGiRQUsnU+9dwPP0IoTdHioTk8H/3j/g== X-Received: by 2002:a17:902:7288:: with SMTP id d8mr21807077pll.341.1576589944270; Tue, 17 Dec 2019 05:39:04 -0800 (PST) Received: from ?IPv6:2402:f000:1:1501:200:5efe:166.111.139.134? ([2402:f000:1:1501:200:5efe:a66f:8b86]) by smtp.gmail.com with ESMTPSA id d2sm3675360pja.1.2019.12.17.05.39.01 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 17 Dec 2019 05:39:03 -0800 (PST) Subject: Re: [BUG] ALSA: seq: a possible sleep-in-atomic-context bug in snd_virmidi_dev_receive_event() To: Takashi Iwai Cc: perex@perex.cz, tiwai@suse.com, rfontana@redhat.com, gregkh@linuxfoundation.org, allison@lohutok.net, tglx@linutronix.de, alsa-devel@alsa-project.org, LKML References: From: Jia-Ju Bai Message-ID: <1583e474-55e3-ec13-f8c9-029bb23971bb@gmail.com> Date: Tue, 17 Dec 2019 21:39:01 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/12/17 21:37, Takashi Iwai wrote: > On Tue, 17 Dec 2019 14:24:21 +0100, > Jia-Ju Bai wrote: >> The driver may sleep while holding a read lock. >> The function call path (from bottom to top) in Linux 4.19 is: >> >> sound/core/seq/seq_memory.c, 96: >>     copy_from_user in snd_seq_dump_var_event >> sound/core/seq/seq_virmidi.c, 97: >>     snd_seq_dump_var_event in snd_virmidi_dev_receive_event >> sound/core/seq/seq_virmidi.c, 88: >>     _raw_read_lock in snd_virmidi_dev_receive_event > This can't happen. snd_virmidi_dev_receive_event() takes > conditionally either read_lock or rw_sem depending on the atomic > argument. And the data including user-space pointer is handled always > with atomic=1, hence down_read() is used instead of read_lock() here. > Okay, thanks for the explanation. Best wishes, Jia-Ju Bai