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 A9BA2C433EF for ; Sat, 7 May 2022 11:06:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1384667AbiEGLKO (ORCPT ); Sat, 7 May 2022 07:10:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43646 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1384661AbiEGLKI (ORCPT ); Sat, 7 May 2022 07:10:08 -0400 Received: from mail-pl1-x630.google.com (mail-pl1-x630.google.com [IPv6:2607:f8b0:4864:20::630]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 91A7A45784; Sat, 7 May 2022 04:06:22 -0700 (PDT) Received: by mail-pl1-x630.google.com with SMTP id q4so6825112plr.11; Sat, 07 May 2022 04:06:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=message-id:date:mime-version:user-agent:subject:to:cc:references :from:in-reply-to:content-transfer-encoding; bh=wESZGcNFKxrpxxsend5gLk245hMJ4SIWUC0qiFaYsPY=; b=qdLpdHS4co9i0tPvHe3i1K7CAJjZC1Tuqwf86FHHH3e999G3pa8SxtITWdKKomC+QB oBt4keJXB0dVVOYVTkEUe9LbuBqza1NCI6k4uKc08YyOFzYWmYH2yu3LIkZuW6WNA6g3 seq3+eM23ea1f1srpMtn0Y1xsZJ4vSbLQWc91Eu2HikxLc6DCZbQbOXZhOY3Y4zW+aGd jhcie0NcYITMFyTdfUQaw+2vWPoyD/4dynind6V1klwL6hjAKkg9WFQFBjdr+oAlg2it tJmSKkQ/kLsAkhYj/EKaMXhXp3bj/gl1DwQuX7QEiimvg1NhRu/ccJfjS85FlH3sz3DF EcCA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :to:cc:references:from:in-reply-to:content-transfer-encoding; bh=wESZGcNFKxrpxxsend5gLk245hMJ4SIWUC0qiFaYsPY=; b=EYEKMn/1MIC1edgAXIbuuILhAPTz4dOfZfuOV7vJlHv2TL0fluLqlZIZb039o50yTd 60iKpM6pcHaKdWYIjOIY9bt4kneRAENxIwPVjlzCnHG08n6x7oOv0BKNIfpSlxuGULpA C13KsKKTGwTjGUH3Q36jj7rccINtpnNQKhLGOkrwN5rv55xejiOONxgPq1aM55xeb8nW um6L/WL5JYHw+TB4MN6TQXDBED7ltg9yvIRrTk/bwg37SMFMtQb9nfjFnIpGbUMC0SQ/ LlvoT/9cJcuT44CKFCJdCV4NKWsiGyT9hyl13xYt+o06E2/RkPt2mE48TnEKNiqagDSX oYzA== X-Gm-Message-State: AOAM530erb8nwgxA6OZbmG5veWJ1TF2DAyQTKTaM955kOmaCDjEeEHR9 P5U2MkFIZwoV2IW5Q54NGyg= X-Google-Smtp-Source: ABdhPJxQiyVuXrP9muBdoqkdc1VjFbALVDVbBdlcrFtkrpXTwWV5bO+ulE2374FZtFiu89j6P5sIdg== X-Received: by 2002:a17:902:9b98:b0:156:52b1:b100 with SMTP id y24-20020a1709029b9800b0015652b1b100mr7977197plp.174.1651921582078; Sat, 07 May 2022 04:06:22 -0700 (PDT) Received: from [192.168.255.10] ([106.53.4.151]) by smtp.gmail.com with ESMTPSA id h2-20020a170902f70200b0015e8d4eb2cbsm3394900plo.277.2022.05.07.04.06.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 07 May 2022 04:06:21 -0700 (PDT) Message-ID: Date: Sat, 7 May 2022 19:06:30 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.9.0 Subject: Re: [PATCH 3/5] io_uring: let fast poll support multishot To: Pavel Begunkov , io-uring@vger.kernel.org Cc: Jens Axboe , linux-kernel@vger.kernel.org References: <20220506070102.26032-1-haoxu.linux@gmail.com> <20220506070102.26032-4-haoxu.linux@gmail.com> <135b16e4-f316-cb25-9cdd-09bd63eb4aef@gmail.com> From: Hao Xu In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2022/5/7 下午5:47, Pavel Begunkov 写道: > On 5/7/22 08:08, Hao Xu wrote: >> 在 2022/5/7 上午1:19, Pavel Begunkov 写道: >>> On 5/6/22 08:01, Hao Xu wrote: > [...] >>> That looks dangerous, io_queue_sqe() usually takes the request ownership >>> and doesn't expect that someone, i.e. io_poll_check_events(), may >>> still be >>> actively using it. >>> >>> E.g. io_accept() fails on fd < 0, return an error, >>> io_queue_sqe() -> io_queue_async() -> io_req_complete_failed() >>> kills it. Then io_poll_check_events() and polling in general >>> carry on using the freed request => UAF. Didn't look at it >>> too carefully, but there might other similar cases. >>> >> I checked this when I did the coding, it seems the only case is >> while (atomic_sub_return(v & IO_POLL_REF_MASK, &req->poll_refs)); >> uses req again after req recycled in io_queue_sqe() path like you >> pointed out above, but this case should be ok since we haven't >> reuse the struct req{} at that point. > > Replied to another message with an example that I think might > be broken, please take a look. I saw it just now, it looks a valid case to me. Thanks. > > The issue is that io_queue_sqe() was always consuming / freeing / > redirecting / etc. requests, i.e. call it and forget about the req. > With io_accept now it may or may not free it and not even returning > any return code about that. This implicit knowledge is quite tricky > to maintain. > > might make more sense to "duplicate" io_queue_sqe() > > ret = io_issue_sqe(req, IO_URING_F_NONBLOCK|IO_URING_F_COMPLETE_DEFER); > // REQ_F_COMPLETE_INLINE should never happen, no check for that > // don't care about io_arm_ltimeout(), should already be armed > // ret handling here This is what I'm doing for v3, indeed make more sense.