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 368BCE748F6 for ; Mon, 2 Oct 2023 16:43:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238210AbjJBQnw (ORCPT ); Mon, 2 Oct 2023 12:43:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59686 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238050AbjJBQns (ORCPT ); Mon, 2 Oct 2023 12:43:48 -0400 Received: from mail-il1-x144.google.com (mail-il1-x144.google.com [IPv6:2607:f8b0:4864:20::144]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 97579197 for ; Mon, 2 Oct 2023 09:43:45 -0700 (PDT) Received: by mail-il1-x144.google.com with SMTP id e9e14a558f8ab-3526ac53d43so1353505ab.1 for ; Mon, 02 Oct 2023 09:43:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20230601.gappssmtp.com; s=20230601; t=1696265025; x=1696869825; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:from:references:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=AMtl0t8ewUYdyp0PrDfhIKqyNakrSyvKX53mRjqJ1tE=; b=AsvpsuzX5OBlNuy47XGRYREwbzmMJbNYSjuYUfnczlL4K9l+K40SrK9FDxfQjuIJI6 DAeSHMGpb9vzMGvB9TH4sAQA9JHqgUmXpU7cVGQhBoDAqFyZIjM9th506DHGUIflEtZJ WdbLXEzGSccuzl+cPlSr9qpOOSv8dRXlqyz7bzReZbgGDP3JATEmryBoKg3M2bBfEFbc izOKP2c+8tFlCW4lYDZA7M/u9+pv6tgM/uHgm+RLMDH0PwNxkeAOlPlM0UpnLLAzp/xG ds4V2flzs6Gk2EiHQO52otdTZ6JlYCHW9e1iW/dF6c02gt5qTRr9gFnX3IBt8paa0CPM aAcA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1696265025; x=1696869825; h=content-transfer-encoding:in-reply-to:from:references:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=AMtl0t8ewUYdyp0PrDfhIKqyNakrSyvKX53mRjqJ1tE=; b=L0moPMq67JA+1vIIXAhrgi4BMQ2gZ/5jp/OrgItgncMDPGoG/mSo8TD42X1dyqmnYn sqyqTf0+rKWAt6+SL5C4Ro81jjGU3k83UGFkpA+AJoce7xuaxUB41eAFnAulwzyJsdwO X1Y7DM7VPR6FIAG8jZPP6AKnkVenjkFz2CKQ9aMlvGZ0W11nZkYCBwtIjJDwOmxIAwc7 vhtQqhXNacMPiFN4MV97sx3YfURCbJiqvJwKjyJYtRfHjKii4Dm4pTVkn5NIQYj3RCq/ 9yN2yKJHJln0pfDQPwtV0AGentstUL8r5s/drI9gp1NJI9YCmc3dPATlFbpufWsWrkHv i3JQ== X-Gm-Message-State: AOJu0YwekddK8RBvQcCy4JvGk1bJhiMvFkV3rPf907v+XGAoeo/2SoZO crMypVcceOb1k+Rv00m9LUoU2w== X-Google-Smtp-Source: AGHT+IFxLlGnk5JYcLuvXJfpCR2uF82ZolgrFATVVixab45nCxnLhXnmWGgUaIVvnmXUehKzsv6Inw== X-Received: by 2002:a92:d487:0:b0:34f:7ba2:50e8 with SMTP id p7-20020a92d487000000b0034f7ba250e8mr11080042ilg.2.1696265024968; Mon, 02 Oct 2023 09:43:44 -0700 (PDT) Received: from [192.168.1.94] ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id r17-20020a92d991000000b0035260e105fdsm2550151iln.36.2023.10.02.09.43.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 02 Oct 2023 09:43:44 -0700 (PDT) Message-ID: <7567c27a-b5d0-41fc-a7e5-d65ed168b39c@kernel.dk> Date: Mon, 2 Oct 2023 10:43:43 -0600 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [syzbot] [io-uring?] BUG: unable to handle kernel NULL pointer dereference in __io_remove_buffers (2) Content-Language: en-US To: syzbot , asml.silence@gmail.com, io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com References: <000000000000af635c0606bcb889@google.com> From: Jens Axboe In-Reply-To: <000000000000af635c0606bcb889@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/2/23 8:38 AM, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: ec8c298121e3 Merge tag 'x86-urgent-2023-10-01' of git://gi.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=16ef0ed6680000 > kernel config: https://syzkaller.appspot.com/x/.config?x=3be743fa9361d5b0 > dashboard link: https://syzkaller.appspot.com/bug?extid=2113e61b8848fa7951d8 > compiler: arm-linux-gnueabi-gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 > userspace arch: arm I tried the syz repro in the console output, but can't trigger it. It also makes very little sense to me... For when there is a reproducer, the below would perhaps shed some light on it. We have bl->is_mapped == 1, yet bl->buf_ring is NULL. Probably some artifact of 32-bit arm? diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c index 556f4df25b0f..d5133ac8005f 100644 --- a/io_uring/kbuf.c +++ b/io_uring/kbuf.c @@ -504,6 +504,9 @@ static int io_pin_pbuf_ring(struct io_uring_buf_reg *reg, return -EINVAL; } #endif + WARN_ON_ONCE(!pages); + WARN_ON_ONCE(!nr_pages); + WARN_ON_ONCE(!br); bl->buf_pages = pages; bl->buf_nr_pages = nr_pages; bl->buf_ring = br; diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c index d9c853d10587..7034be555334 100644 --- a/io_uring/rsrc.c +++ b/io_uring/rsrc.c @@ -1037,39 +1037,36 @@ struct page **io_pin_pages(unsigned long ubuf, unsigned long len, int *npages) { unsigned long start, end, nr_pages; struct page **pages = NULL; - int pret, ret = -ENOMEM; + int ret; end = (ubuf + len + PAGE_SIZE - 1) >> PAGE_SHIFT; start = ubuf >> PAGE_SHIFT; nr_pages = end - start; + WARN_ON(!nr_pages); pages = kvmalloc_array(nr_pages, sizeof(struct page *), GFP_KERNEL); if (!pages) - goto done; + return ERR_PTR(-ENOMEM); - ret = 0; mmap_read_lock(current->mm); - pret = pin_user_pages(ubuf, nr_pages, FOLL_WRITE | FOLL_LONGTERM, - pages); - if (pret == nr_pages) + ret = pin_user_pages(ubuf, nr_pages, FOLL_WRITE | FOLL_LONGTERM, pages); + mmap_read_unlock(current->mm); + + /* success, mapped all pages */ + if (ret == nr_pages) { *npages = nr_pages; - else - ret = pret < 0 ? pret : -EFAULT; + return pages; + } - mmap_read_unlock(current->mm); - if (ret) { + /* partial map, or didn't map anything */ + if (ret >= 0) { /* if we did partial map, release any pages we did get */ - if (pret > 0) - unpin_user_pages(pages, pret); - goto done; - } - ret = 0; -done: - if (ret < 0) { - kvfree(pages); - pages = ERR_PTR(ret); + if (ret) + unpin_user_pages(pages, ret); + ret = -EFAULT; } - return pages; + kvfree(pages); + return ERR_PTR(ret); } static int io_sqe_buffer_register(struct io_ring_ctx *ctx, struct iovec *iov, -- Jens Axboe