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From: Ryusuke Konishi <konishi.ryusuke@gmail.com>
To: Peng Zhang <zhangpeng362@huawei.com>
Cc: ye.xingchen@zte.com.cn, chi.minghao@zte.com.cn,
	vishal.moola@gmail.com, linux-nilfs@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	syzbot+ebe05ee8e98f755f61d0@syzkaller.appspotmail.com
Subject: Re: [PATCH] nilfs2: fix NULL pointer dereference in nilfs_palloc_commit_free_entry()
Date: Sat, 19 Nov 2022 10:02:05 +0900	[thread overview]
Message-ID: <CAKFNMomd9j3o1iQN6kyUoDcEKGwh34CqAjAWeF5g_s8eSEVX5Q@mail.gmail.com> (raw)
In-Reply-To: <CAKFNMonXdyMw9mrQeGe_KtSfMDPSC_jNai8FZGceVyV9Nxw8AQ@mail.gmail.com>

On Sat, Nov 19, 2022 at 9:38 AM Ryusuke Konishi wrote:
> On Tue, Nov 15, 2022 at 3:39 AM Ryusuke Konishi  wrote:
> > On Mon, Nov 14, 2022 at 12:39 PM Peng Zhang wrote:
> What was happening here was complicated.
> There were two state inconsistencies in DAT:
> 1) A virtual block number (vblocknr == 6145) in the report, was used
> twice in a btree.
>     Because of this, nilfs_dat_commit_end() on that address was called twice.
> 2) For the virtual block number (vblocknr == 6145), the DAT bitmap
> status was free (second anomaly), and nilfs_dat_commit_alloc() was
> performed at the same time as the second nilfs_dat_commit_end() above.
>
> As I mentioned, when nilfs_dat_commit_end() frees a virtual block
> number in the bitmap of DAT, nilfs_dat_prepare_end() usually allocates
> buffer heads of the bitmap block and the descriptor block, and sets
> them to the request struct.  But, the above two anomalies overlap, as

> you pointed out, de_block is initialized to 0 by
> nilfs_dat_prepare_alloc() in the middle of "prepare" and "commit", and

I wrote it wrong, this should be ".., de_blocknr is initialized to 0
by nilfs_dat_commit_alloc() ..".

Ryusuke Konishi

WARNING: multiple messages have this Message-ID (diff)
From: Ryusuke Konishi <konishi.ryusuke-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: Peng Zhang <zhangpeng362-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
Cc: ye.xingchen-Th6q7B73Y6EnDS1+zs4M5A@public.gmane.org,
	chi.minghao-Th6q7B73Y6EnDS1+zs4M5A@public.gmane.org,
	vishal.moola-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org,
	linux-nilfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	syzbot+ebe05ee8e98f755f61d0-Pl5Pbv+GP7P466ipTTIvnc23WoclnBCfAL8bYrjMMd8@public.gmane.org
Subject: Re: [PATCH] nilfs2: fix NULL pointer dereference in nilfs_palloc_commit_free_entry()
Date: Sat, 19 Nov 2022 10:02:05 +0900	[thread overview]
Message-ID: <CAKFNMomd9j3o1iQN6kyUoDcEKGwh34CqAjAWeF5g_s8eSEVX5Q@mail.gmail.com> (raw)
In-Reply-To: <CAKFNMonXdyMw9mrQeGe_KtSfMDPSC_jNai8FZGceVyV9Nxw8AQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>

On Sat, Nov 19, 2022 at 9:38 AM Ryusuke Konishi wrote:
> On Tue, Nov 15, 2022 at 3:39 AM Ryusuke Konishi  wrote:
> > On Mon, Nov 14, 2022 at 12:39 PM Peng Zhang wrote:
> What was happening here was complicated.
> There were two state inconsistencies in DAT:
> 1) A virtual block number (vblocknr == 6145) in the report, was used
> twice in a btree.
>     Because of this, nilfs_dat_commit_end() on that address was called twice.
> 2) For the virtual block number (vblocknr == 6145), the DAT bitmap
> status was free (second anomaly), and nilfs_dat_commit_alloc() was
> performed at the same time as the second nilfs_dat_commit_end() above.
>
> As I mentioned, when nilfs_dat_commit_end() frees a virtual block
> number in the bitmap of DAT, nilfs_dat_prepare_end() usually allocates
> buffer heads of the bitmap block and the descriptor block, and sets
> them to the request struct.  But, the above two anomalies overlap, as

> you pointed out, de_block is initialized to 0 by
> nilfs_dat_prepare_alloc() in the middle of "prepare" and "commit", and

I wrote it wrong, this should be ".., de_blocknr is initialized to 0
by nilfs_dat_commit_alloc() ..".

Ryusuke Konishi

  reply	other threads:[~2022-11-19  1:45 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-14  4:04 [PATCH] nilfs2: fix NULL pointer dereference in nilfs_palloc_commit_free_entry() Peng Zhang
2022-11-14  4:04 ` Peng Zhang
2022-11-14 18:39 ` Ryusuke Konishi
2022-11-14 18:39   ` Ryusuke Konishi
2022-11-19  0:38   ` Ryusuke Konishi
2022-11-19  0:38     ` Ryusuke Konishi
2022-11-19  1:02     ` Ryusuke Konishi [this message]
2022-11-19  1:02       ` Ryusuke Konishi
     [not found]     ` <422d9c54-a119-b2a2-f381-11f83af3d9ea@huawei.com>
2022-11-19  7:24       ` Ryusuke Konishi
2022-11-19  7:24         ` Ryusuke Konishi

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