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=-15.5 required=3.0 tests=BAYES_00,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 29739C433E0 for ; Fri, 19 Feb 2021 09:18:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D2F2564DED for ; Fri, 19 Feb 2021 09:18:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229862AbhBSJSn (ORCPT ); Fri, 19 Feb 2021 04:18:43 -0500 Received: from mail-ej1-f44.google.com ([209.85.218.44]:37479 "EHLO mail-ej1-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229527AbhBSJSj (ORCPT ); Fri, 19 Feb 2021 04:18:39 -0500 Received: by mail-ej1-f44.google.com with SMTP id d8so11383925ejc.4 for ; Fri, 19 Feb 2021 01:18:23 -0800 (PST) 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-language :content-transfer-encoding; bh=P7plXYyBJGEyQFVaumgZw2bPyhz33gTigGSr4ns5JY8=; b=cdIBruiLzHeeNVM/taZ06J0bqTMQPmqJPQsFKTn/vtp0T2LW/Q8653vuBxsVEXwQ4Y F0OI6p5VCrhywruUX3D+JjBYRBjj4SUwsUnCSrRNAZY37EiGtB4swcB90v4QhH8J1Eq7 TQATZSypzXi35N4XRF8jVjA3C0Jf4g+3bz52Q/41kMHeKC21MQwE2h09QyKIYYUNmuFG RKDgRaIsBnydeFgPU6ToV/HD3xUHT5Ox1WgwOjb3hpMIotDR/B7KIL6UfNJVSxOoXM/o tjvLfZxRBvPc3oJgKM3ITLJhR6ILdV0aDBKflZ3pl3lYyIGskv678RWnEn0GOiHCAPUn 6k9Q== X-Gm-Message-State: AOAM531SDGdOy1Qg15kSL9P3pUAKDTj6PGDrWBLSdGoWvnRh0WF9J24P bmcs5ZFAOvSmBhwBlcnswKE= X-Google-Smtp-Source: ABdhPJw1AwT98wHTLcvrL5MaF0jmJGxMjUhMWocE2wkYxtIet7qI/kOvRFkQLTtsnw6wWsBkmOML8g== X-Received: by 2002:a17:906:7119:: with SMTP id x25mr5128009ejj.362.1613726277515; Fri, 19 Feb 2021 01:17:57 -0800 (PST) Received: from ?IPv6:2a0b:e7c0:0:107::49? ([2a0b:e7c0:0:107::49]) by smtp.gmail.com with ESMTPSA id s12sm4487828edu.28.2021.02.19.01.17.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 19 Feb 2021 01:17:56 -0800 (PST) Subject: Re: [PATCH v2] tty: fix when iov_iter_count() returns 0 in tty_write() To: Sabyrzhan Tasbolatov , gregkh@linuxfoundation.org Cc: linux-kernel@vger.kernel.org, syzbot+3d2c27c2b7dc2a94814d@syzkaller.appspotmail.com References: <20210217155536.2986178-1-snovitoll@gmail.com> From: Jiri Slaby Message-ID: Date: Fri, 19 Feb 2021 10:17:55 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <20210217155536.2986178-1-snovitoll@gmail.com> Content-Type: text/plain; charset=iso-8859-2; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 17. 02. 21, 16:55, Sabyrzhan Tasbolatov wrote: > syzbot found WARNING in iov_iter_revert[1] when iov_iter_count() returns 0, > therefore INT_MAX is passed to iov_iter_revert() causing > MAX_RW_COUNT > warning. > > static inline ssize_t do_tty_write() > { > .. > size_t count = iov_iter_count(from); > .. > size_t size = count; > if (ret != size) > iov_iter_revert(from, size-ret); > > [1] WARNING: lib/iov_iter.c:1090 > Call Trace: > do_tty_write drivers/tty/tty_io.c:967 [inline] > file_tty_write.constprop.0+0x55f/0x8f0 drivers/tty/tty_io.c:1048 > call_write_iter include/linux/fs.h:1901 [inline] > new_sync_write+0x426/0x650 fs/read_write.c:518 > vfs_write+0x791/0xa30 fs/read_write.c:605 > ksys_write+0x12d/0x250 fs/read_write.c:658 > > Fixes: 9bb48c82aced ("tty: implement write_iter") > Reported-by: syzbot+3d2c27c2b7dc2a94814d@syzkaller.appspotmail.com > Signed-off-by: Sabyrzhan Tasbolatov > --- > > v2: Fixed "Fixed" tag to proper commit and changed write return to -EFAULT > as this statement is valid, tested via strace: > > write(3, NULL, 0) = -1 EFAULT (Bad address) > > Updated to -EFAULT, should be a valid exit code as > copy_from_iter(.., .., from) returns -EFAULT as well if *from is invalid > address. Exactly, EFAULT is for invalid memory accesses. But this should be IMO EINVAL as it's an invalid argument. BTW what's the reason vfs calls ->write with zero count of iter? >> Nit, you need a ' ' before your '(' character here, otherwise the >> linux-next scripts will complain. > >> Also, you got the git commit id wrong, so this needs to be fixed up >> anyway. You are pointing to a merge point, I doubt that's what you want >> to point to here, right? > > Thanks! > --- > drivers/tty/tty_io.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c > index 816e709afa56..e1460cad8b7d 100644 > --- a/drivers/tty/tty_io.c > +++ b/drivers/tty/tty_io.c > @@ -905,6 +905,9 @@ static inline ssize_t do_tty_write( > ssize_t ret, written = 0; > unsigned int chunk; > > + if (!count) > + return -EFAULT; > + > ret = tty_write_lock(tty, file->f_flags & O_NDELAY); > if (ret < 0) > return ret; > -- js