From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@kernel.org>
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 14B46C433F5
	for <linux-kernel@archiver.kernel.org>; Sun, 12 Dec 2021 09:15:10 +0000 (UTC)
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S229966AbhLLJPI (ORCPT <rfc822;linux-kernel@archiver.kernel.org>);
        Sun, 12 Dec 2021 04:15:08 -0500
Received: from ams.source.kernel.org ([145.40.68.75]:44054 "EHLO
        ams.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S229956AbhLLJPG (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Sun, 12 Dec 2021 04:15:06 -0500
Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140])
        (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
        (No client certificate requested)
        by ams.source.kernel.org (Postfix) with ESMTPS id 69955B80B8F
        for <linux-kernel@vger.kernel.org>; Sun, 12 Dec 2021 09:15:05 +0000 (UTC)
Received: by smtp.kernel.org (Postfix) with ESMTPSA id E7660C341C6;
        Sun, 12 Dec 2021 09:15:01 +0000 (UTC)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org;
        s=k20201202; t=1639300504;
        bh=vLxxgiN0imWkT8KfiHgu08g5fJXl0/viq5uHLPUJ5SM=;
        h=Date:Subject:To:Cc:References:From:In-Reply-To:From;
        b=QFlQM4qMyz1cklOPUeW6tPx2tCzGaG/5zH6dwDEWR1a3ZnitKeiHEdoPR/k3GdIx9
         xtJi28g109rkIDdCZDJGr4mmqgu+wjV5D9GBplCyehOPPQSys8pYWZNj5R+MKzk8/2
         rhzvoIbjz4BO4NdtudZ+ImeZZiEPInspxOaP8sfxdH1oJl63oOBOpKiaTVpXovCbvz
         iRb1Gr+1k+Ijdx+ayKvQIbaIaB056wQDuOl2LmsXn3zGNRKJ0hUtQKrJ55uoaN4LTM
         QrN7Axv7z9NnW7VojO2VCZprEh/n4//KuVXdT8GwCtZtFIgsi38pRYWPw8N4+hWUHS
         hMUCc4bV9qcHA==
Message-ID: <51598d4d-0136-4a41-6b06-fbd7221ffd0e@kernel.org>
Date:   Sun, 12 Dec 2021 17:15:00 +0800
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101
 Thunderbird/91.4.0
Subject: Re: [f2fs-dev] [syzbot] BUG: unable to handle kernel NULL pointer
 dereference in folio_mark_dirty
Content-Language: en-US
To:     Jaegeuk Kim <jaegeuk@kernel.org>,
        Matthew Wilcox <willy@infradead.org>
Cc:     syzbot <syzbot+7cd473c2cac13fd2dd72@syzkaller.appspotmail.com>,
        syzkaller-bugs@googlegroups.com, linux-kernel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net, linux-mm@kvack.org,
        Andrew Morton <akpm@linux-foundation.org>
References: <0000000000005f297e05d24f05f6@google.com>
 <20211206175631.5d0c3caefa96f0479f0fc2e8@linux-foundation.org>
 <Ya7jYRDwQqftGLtW@casper.infradead.org> <Ya/Ueh7MWyvV2zdg@google.com>
 <Ya/ZaxznaTmrIvdO@casper.infradead.org> <Ya/bviwnMPsSnOcy@google.com>
From:   Chao Yu <chao@kernel.org>
In-Reply-To: <Ya/bviwnMPsSnOcy@google.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 2021/12/8 6:10, Jaegeuk Kim wrote:
> On 12/07, Matthew Wilcox wrote:
>> On Tue, Dec 07, 2021 at 01:39:06PM -0800, Jaegeuk Kim wrote:
>>> On 12/07, Matthew Wilcox wrote:
>>>>>> Call Trace:
>>>>>>   <TASK>
>>>>>>   folio_mark_dirty+0x136/0x270 mm/page-writeback.c:2639
>>>>
>>>>          if (likely(mapping)) {
>>>> ...
>>>>                  if (folio_test_reclaim(folio))
>>>>                          folio_clear_reclaim(folio);
>>>>                  return mapping->a_ops->set_page_dirty(&folio->page);
>>>>
>>>> how do we get to a NULL ->set_page_dirty for a metadata page's
>>>> mapping->a_ops?  This is definitely an f2fs expert question.
>>>
>>> I can't find anything in f2fs, since that page was got by f2fs_grab_meta_page
>>> along with grab_cache_page() that we never unlocked it.
>>>
>>>    40 struct page *f2fs_grab_meta_page(struct f2fs_sb_info *sbi, pgoff_t index)
>>>    41 {
>>>    42         struct address_space *mapping = META_MAPPING(sbi);
>>>    43         struct page *page;
>>>    44 repeat:
>>>    45         page = f2fs_grab_cache_page(mapping, index, false);
>>>
>>>                      -> grab_cache_page(mapping, index);
>>>
>>>    46         if (!page) {
>>>    47                 cond_resched();
>>>    48                 goto repeat;
>>>    49         }
>>>    50         f2fs_wait_on_page_writeback(page, META, true, true);
>>>    51         if (!PageUptodate(page))
>>>    52                 SetPageUptodate(page);
>>>    53         return page;
>>>    54 }
>>>
>>>
>>> Suspecting something in folio wrt folio_mapping()?
>>>
>>>   81 bool set_page_dirty(struct page *page)
>>>   82 {
>>>   83         return folio_mark_dirty(page_folio(page));
>>>   84 }
>>
>> ... huh?  How could folio_mapping() be getting this wrong?
> 
> Dunno.
> 
>> page_folio() does the same thing as compound_head() -- as far as I know
>> you don't use compound pages for f2fs metadata, so this basically just
>> casts the page to a struct folio.
>>
>> folio_mapping() is just like the old page_mapping() (see commit
>> 2f52578f9c64).  Unless you've done something like set the swapcache
>> bit on your metadata page, it's just going to return folio->mapping
>> (ie the same as page->mapping).
> 
> Hmm, I've never seen this call stack before, so simply started to suspect
> folio.

I'm afraid this is a f2fs bug... :(

folio wasn't merged at the first report time (5.14-rc2).

https://syzkaller.appspot.com/bug?extid=07ff38c9c93ca170de07

I doubt the direct reason of panic may be the same as the one of bug
reported in bugzilla:

https://bugzilla.kernel.org/show_bug.cgi?id=215231

However, I still can't figure out why meta_inode's a_ops will change
to f2fs_meta_aops.

Thanks,

> 
> 
> _______________________________________________
> Linux-f2fs-devel mailing list
> Linux-f2fs-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel

From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-f2fs-devel-bounces@lists.sourceforge.net>
X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on
	aws-us-west-2-korg-lkml-1.web.codeaurora.org
Received: from lists.sourceforge.net (lists.sourceforge.net [216.105.38.7])
	(using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
	(No client certificate requested)
	by smtp.lore.kernel.org (Postfix) with ESMTPS id 6B2D4C433EF
	for <linux-f2fs-devel@archiver.kernel.org>; Sun, 12 Dec 2021 09:15:22 +0000 (UTC)
Received: from [127.0.0.1] (helo=sfs-ml-4.v29.lw.sourceforge.com)
	by sfs-ml-4.v29.lw.sourceforge.com with esmtp (Exim 4.94.2)
	(envelope-from <linux-f2fs-devel-bounces@lists.sourceforge.net>)
	id 1mwKww-0006Hd-VN; Sun, 12 Dec 2021 09:15:18 +0000
Received: from [172.30.20.202] (helo=mx.sourceforge.net)
 by sfs-ml-4.v29.lw.sourceforge.com with esmtps (TLS1.2) tls
 TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2)
 (envelope-from <chao@kernel.org>) id 1mwKwu-0006HX-HP
 for linux-f2fs-devel@lists.sourceforge.net; Sun, 12 Dec 2021 09:15:16 +0000
DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed;
 d=sourceforge.net; s=x; h=Content-Transfer-Encoding:Content-Type:In-Reply-To:
 From:References:Cc:To:Subject:MIME-Version:Date:Message-ID:Sender:Reply-To:
 Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender:
 Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:
 List-Subscribe:List-Post:List-Owner:List-Archive;
 bh=HgAiB9G9sqR7Ltc7ikhydbkv5MWf6UASHljtuglqmZo=; b=KNMP8TsjHaXdKLGTpkwtQo1f1A
 mpxnYwi8TpbdCJfljJ31RfGaE8zukOC50SnusR49fL/4Yp29A07xUHxRHokJcerlBvvfpixJZ3IAG
 7vdqjjzFYcNCi+uQVAq3nzN35T4zSafvipz+FJR0u/U6vv/2jI//1eruSfIIRELmxqno=;
DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sf.net; s=x
 ;
 h=Content-Transfer-Encoding:Content-Type:In-Reply-To:From:References:Cc:To:
 Subject:MIME-Version:Date:Message-ID:Sender:Reply-To:Content-ID:
 Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc
 :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe:
 List-Post:List-Owner:List-Archive;
 bh=HgAiB9G9sqR7Ltc7ikhydbkv5MWf6UASHljtuglqmZo=; b=U/t+zSCV+05qbYAvHlfORTqBpx
 Ov0B2frkF/1fOaiSHMWoAiJebBmBL7MicpDJ/kaWswzPHhs86NhPDDSNVyCk4mJHl+aK8peWHN8eP
 GyDkomHYzOM3LycsX1LyJEtmDU1j4hA9ZZM4FQtgfbmjCBlyxCu1FA3LsR7QoSVPNTV8=;
Received: from ams.source.kernel.org ([145.40.68.75])
 by sfi-mx-2.v28.lw.sourceforge.com with esmtps
 (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.92.3)
 id 1mwKwp-0003of-Qg
 for linux-f2fs-devel@lists.sourceforge.net; Sun, 12 Dec 2021 09:15:16 +0000
Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140])
 (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
 (No client certificate requested)
 by ams.source.kernel.org (Postfix) with ESMTPS id 75A2DB80B90;
 Sun, 12 Dec 2021 09:15:05 +0000 (UTC)
Received: by smtp.kernel.org (Postfix) with ESMTPSA id E7660C341C6;
 Sun, 12 Dec 2021 09:15:01 +0000 (UTC)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org;
 s=k20201202; t=1639300504;
 bh=vLxxgiN0imWkT8KfiHgu08g5fJXl0/viq5uHLPUJ5SM=;
 h=Date:Subject:To:Cc:References:From:In-Reply-To:From;
 b=QFlQM4qMyz1cklOPUeW6tPx2tCzGaG/5zH6dwDEWR1a3ZnitKeiHEdoPR/k3GdIx9
 xtJi28g109rkIDdCZDJGr4mmqgu+wjV5D9GBplCyehOPPQSys8pYWZNj5R+MKzk8/2
 rhzvoIbjz4BO4NdtudZ+ImeZZiEPInspxOaP8sfxdH1oJl63oOBOpKiaTVpXovCbvz
 iRb1Gr+1k+Ijdx+ayKvQIbaIaB056wQDuOl2LmsXn3zGNRKJ0hUtQKrJ55uoaN4LTM
 QrN7Axv7z9NnW7VojO2VCZprEh/n4//KuVXdT8GwCtZtFIgsi38pRYWPw8N4+hWUHS
 hMUCc4bV9qcHA==
Message-ID: <51598d4d-0136-4a41-6b06-fbd7221ffd0e@kernel.org>
Date: Sun, 12 Dec 2021 17:15:00 +0800
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101
 Thunderbird/91.4.0
Content-Language: en-US
To: Jaegeuk Kim <jaegeuk@kernel.org>, Matthew Wilcox <willy@infradead.org>
References: <0000000000005f297e05d24f05f6@google.com>
 <20211206175631.5d0c3caefa96f0479f0fc2e8@linux-foundation.org>
 <Ya7jYRDwQqftGLtW@casper.infradead.org> <Ya/Ueh7MWyvV2zdg@google.com>
 <Ya/ZaxznaTmrIvdO@casper.infradead.org> <Ya/bviwnMPsSnOcy@google.com>
From: Chao Yu <chao@kernel.org>
In-Reply-To: <Ya/bviwnMPsSnOcy@google.com>
X-Headers-End: 1mwKwp-0003of-Qg
Subject: Re: [f2fs-dev] [syzbot] BUG: unable to handle kernel NULL pointer
 dereference in folio_mark_dirty
X-BeenThere: linux-f2fs-devel@lists.sourceforge.net
X-Mailman-Version: 2.1.21
Precedence: list
List-Id: <linux-f2fs-devel.lists.sourceforge.net>
List-Unsubscribe: <https://lists.sourceforge.net/lists/options/linux-f2fs-devel>, 
 <mailto:linux-f2fs-devel-request@lists.sourceforge.net?subject=unsubscribe>
List-Archive: <http://sourceforge.net/mailarchive/forum.php?forum_name=linux-f2fs-devel>
List-Post: <mailto:linux-f2fs-devel@lists.sourceforge.net>
List-Help: <mailto:linux-f2fs-devel-request@lists.sourceforge.net?subject=help>
List-Subscribe: <https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel>, 
 <mailto:linux-f2fs-devel-request@lists.sourceforge.net?subject=subscribe>
Cc: syzbot <syzbot+7cd473c2cac13fd2dd72@syzkaller.appspotmail.com>,
 syzkaller-bugs@googlegroups.com, linux-kernel@vger.kernel.org,
 linux-f2fs-devel@lists.sourceforge.net, linux-mm@kvack.org,
 Andrew Morton <akpm@linux-foundation.org>
Content-Transfer-Encoding: 7bit
Content-Type: text/plain; charset="us-ascii"; Format="flowed"
Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net

On 2021/12/8 6:10, Jaegeuk Kim wrote:
> On 12/07, Matthew Wilcox wrote:
>> On Tue, Dec 07, 2021 at 01:39:06PM -0800, Jaegeuk Kim wrote:
>>> On 12/07, Matthew Wilcox wrote:
>>>>>> Call Trace:
>>>>>>   <TASK>
>>>>>>   folio_mark_dirty+0x136/0x270 mm/page-writeback.c:2639
>>>>
>>>>          if (likely(mapping)) {
>>>> ...
>>>>                  if (folio_test_reclaim(folio))
>>>>                          folio_clear_reclaim(folio);
>>>>                  return mapping->a_ops->set_page_dirty(&folio->page);
>>>>
>>>> how do we get to a NULL ->set_page_dirty for a metadata page's
>>>> mapping->a_ops?  This is definitely an f2fs expert question.
>>>
>>> I can't find anything in f2fs, since that page was got by f2fs_grab_meta_page
>>> along with grab_cache_page() that we never unlocked it.
>>>
>>>    40 struct page *f2fs_grab_meta_page(struct f2fs_sb_info *sbi, pgoff_t index)
>>>    41 {
>>>    42         struct address_space *mapping = META_MAPPING(sbi);
>>>    43         struct page *page;
>>>    44 repeat:
>>>    45         page = f2fs_grab_cache_page(mapping, index, false);
>>>
>>>                      -> grab_cache_page(mapping, index);
>>>
>>>    46         if (!page) {
>>>    47                 cond_resched();
>>>    48                 goto repeat;
>>>    49         }
>>>    50         f2fs_wait_on_page_writeback(page, META, true, true);
>>>    51         if (!PageUptodate(page))
>>>    52                 SetPageUptodate(page);
>>>    53         return page;
>>>    54 }
>>>
>>>
>>> Suspecting something in folio wrt folio_mapping()?
>>>
>>>   81 bool set_page_dirty(struct page *page)
>>>   82 {
>>>   83         return folio_mark_dirty(page_folio(page));
>>>   84 }
>>
>> ... huh?  How could folio_mapping() be getting this wrong?
> 
> Dunno.
> 
>> page_folio() does the same thing as compound_head() -- as far as I know
>> you don't use compound pages for f2fs metadata, so this basically just
>> casts the page to a struct folio.
>>
>> folio_mapping() is just like the old page_mapping() (see commit
>> 2f52578f9c64).  Unless you've done something like set the swapcache
>> bit on your metadata page, it's just going to return folio->mapping
>> (ie the same as page->mapping).
> 
> Hmm, I've never seen this call stack before, so simply started to suspect
> folio.

I'm afraid this is a f2fs bug... :(

folio wasn't merged at the first report time (5.14-rc2).

https://syzkaller.appspot.com/bug?extid=07ff38c9c93ca170de07

I doubt the direct reason of panic may be the same as the one of bug
reported in bugzilla:

https://bugzilla.kernel.org/show_bug.cgi?id=215231

However, I still can't figure out why meta_inode's a_ops will change
to f2fs_meta_aops.

Thanks,

> 
> 
> _______________________________________________
> Linux-f2fs-devel mailing list
> Linux-f2fs-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel


_______________________________________________
Linux-f2fs-devel mailing list
Linux-f2fs-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel