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Message-ID: <d96c776b-20de-c653-a032-bbd3f1df1793@huawei.com>
Date: Fri, 13 Mar 2020 16:15:46 +0800
From: lishan <lishan24@...wei.com>
To: Joseph Qi <joseph.qi@...ux.alibaba.com>,
Mark Fasheh <mark@...heh.com>,
Joel Becker <jlbec@...lplan.org>, Jan Kara <jack@...e.com>
CC: piao jun <piaojun@...wei.com>,
ocfs2-devel <ocfs2-devel@....oracle.com>,
linux ext4 <linux-ext4@...r.kernel.org>,
linux kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ocfs2: fix a null pointer derefrence in
ocfs2_block_group_clear_bits()
ping ?
to Jan Kara
On 2020/3/12 10:38, lishan wrote:
> Hi, Jan Kara:
>
> I have a long-standing problem,
> In the ocfs2 file system, there is a panic problem related to b_committed_data,
> details can be found in the historical mail.
>
> Refer to the old version of the ext3 file system,
> ocfs2 file system uses the undo process to ensure that metadata
> which is not committed to disk is not reused.
>
> I understand that for transactions that have not been committed,
> b_committed_data will not be NULL, so,
> in what scenario do you think b_committed_data will be set to NULL?
>
> Thanks,
> Shan
>
> On 2020/3/11 9:15, Joseph Qi wrote:
>>
>>
>> On 2020/3/9 16:26, lishan wrote:
>>> A NULL pointer panic dereference in ocfs2_block_group_clear_bits() happen again.
>>> The information of NULL pointer stack as follows:
>>>
>>> PID: 81866 TASK: ffffa07c3c21ae80 CPU: 66 COMMAND: "fallocate"
>>> #0 [ffff0000b4d6b0b0] machine_kexec at ffff0000800a2954
>>> #1 [ffff0000b4d6b110] __crash_kexec at ffff0000801bab34
>>> #2 [ffff0000b4d6b2a0] panic at ffff0000800f02cc
>>> #3 [ffff0000b4d6b380] die at ffff00008008f6ac
>>> #4 [ffff0000b4d6b3d0] bug_handler at ffff00008008f744
>>> #5 [ffff0000b4d6b400] brk_handler at ffff000080085d1c
>>> #6 [ffff0000b4d6b420] do_debug_exception at ffff000080081194
>>> #7 [ffff0000b4d6b630] el1_dbg at ffff00008008332c
>>> PC: ffff00000190e9c0 [_ocfs2_free_suballoc_bits+1608]
>>> LR: ffff00000190e990 [_ocfs2_free_suballoc_bits+1560]
>>> SP: ffff0000b4d6b640 PSTATE: 60400009
>>> X29: ffff0000b4d6b650 X28: 0000000000000000 X27: 00000000000052f3
>>> X26: ffff807c511a9570 X25: ffff807ca0054000 X24: 00000000000052f2
>>> X23: 0000000000000001 X22: ffff807c7cde7a90 X21: ffff0000811d9000
>>> X20: ffff807c5e7d2000 X19: ffff00000190c768 X18: 0000000000000000
>>> X17: 0000000000000000 X16: ffff000080a032f0 X15: 0000000000000000
>>> X14: ffffffffffffffff X13: fffffffffffffff7 X12: ffffffffffffffff
>>> X11: 0000000000000038 X10: 0101010101010101 X9: ffffffffffffffff
>>> X8: 7f7f7f7f7f7f7f7f X7: 0000000000000000 X6: 0000000000000080
>>> X5: 0000000000000000 X4: 0000000000000002 X3: ffff00000199f390
>>> X2: a603c08321456e00 X1: ffff807c7cde7a90 X0: 0000000000000000
>>> #8 [ffff0000b4d6b650] _ocfs2_free_suballoc_bits at ffff00000190e9bc [ocfs2]
>>> #9 [ffff0000b4d6b710] _ocfs2_free_clusters at ffff0000019110d4 [ocfs2]
>>> #10 [ffff0000b4d6b790] ocfs2_free_clusters at ffff000001913e94 [ocfs2]
>>> #11 [ffff0000b4d6b7d0] __ocfs2_flush_truncate_log at ffff0000018b5294 [ocfs2]
>>> #12 [ffff0000b4d6b8a0] ocfs2_remove_btree_range at ffff0000018bb34c [ocfs2]
>>> #13 [ffff0000b4d6b960] ocfs2_commit_truncate at ffff0000018bc76c [ocfs2]
>>> #14 [ffff0000b4d6ba60] ocfs2_wipe_inode at ffff0000018e57bc [ocfs2]
>>> #15 [ffff0000b4d6bb00] ocfs2_evict_inode at ffff0000018e5db8 [ocfs2]
>>> #16 [ffff0000b4d6bb70] evict at ffff000080365040
>>> #17 [ffff0000b4d6bba0] iput at ffff0000803655d8
>>> #18 [ffff0000b4d6bbe0] ocfs2_dentry_iput at ffff0000018c60a0 [ocfs2]
>>> #19 [ffff0000b4d6bc30] dentry_unlink_inode at ffff00008035ef58
>>> #20 [ffff0000b4d6bc50] __dentry_kill at ffff000080360384
>>> #21 [ffff0000b4d6bc80] dentry_kill at ffff000080360670
>>> #22 [ffff0000b4d6bcb0] dput at ffff00008036093c
>>> #23 [ffff0000b4d6bcf0] __fput at ffff000080343930
>>> #24 [ffff0000b4d6bd40] ____fput at ffff000080343aac
>>> #25 [ffff0000b4d6bd60] task_work_run at ffff0000801172fc
>>>
>>> The direct panic reason is that bh2jh (group_bh)-> b_committed_data is null.
>>> It is presumed that the network was disconnected during the write process,
>>> causing the transaction abort. as follows:
>>> jbd2_journal_abort
>>> .......
>>> jbd2_journal_commit_transaction
>>> jh->b_committed_data = NULL;
>>>
>>> _ocfs2_free_suballoc_bits
>>> ocfs2_block_group_clear_bits
>>> // undo_bg is now set to null
>>> BUG_ON(!undo_bg);
>>>
>>> When applying for free space, if b_committed_data is null,
>>> it will be directly occupied, as follows:
>>> ocfs2_cluster_group_search
>>> ocfs2_block_group_find_clear_bits
>>> ocfs2_test_bg_bit_allocatable:
>>> bg = (struct ocfs2_group_desc *) bh2jh(bg_bh)->b_committed_data;
>>> if (bg)
>>> ret = !ocfs2_test_bit(nr, (unsigned long *)bg->bg_bitmap);
>>> else
>>> ret = 1;
>>> b_committed_data is an intermediate state backup for bitmap transaction commits,
>>> newly applied space can overwrite previous dirty data,
>>> so, I think, while free clusters, if b_committed_data is null, ignore it.
>>> Host panic directly, too violent.
>>>
>>> Signed-off-by: Shan Li <lishan24@...wei.com>
>>> Reviewed-by: Jun Piao <piaojun@...wei.com>
>>> ---
>>> fs/ocfs2/suballoc.c | 9 +++++++--
>>> 1 file changed, 7 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/fs/ocfs2/suballoc.c b/fs/ocfs2/suballoc.c
>>> index 939df99d2dec..aaf1b3cbd984 100644
>>> --- a/fs/ocfs2/suballoc.c
>>> +++ b/fs/ocfs2/suballoc.c
>>> @@ -2412,14 +2412,19 @@ static int ocfs2_block_group_clear_bits(handle_t *handle,
>>> if (undo_fn) {
>>> spin_lock(&jh->b_state_lock);
>>> undo_bg = (struct ocfs2_group_desc *) jh->b_committed_data;
>>> - BUG_ON(!undo_bg);
>>> + if (!undo_bg)
>>> + mlog(ML_NOTICE, "%s: group descriptor # %llu (device %s) journal "
>>> + "b_committed_data had been cleared.\n",
>>> + OCFS2_SB(alloc_inode->i_sb)->uuid_str,
>>> + (unsigned long long)le64_to_cpu(bg->bg_blkno),
>>> + alloc_inode->i_sb->s_id);
>>
>> Seems a kind of workaround.
>> I am worrying about other abnormal cases of NULL b_committed_data, it
>> may lead to a corrupt filesystem.
>> So how about isolating the journal abort case?
>>
>> Thanks,
>> Joseph
>>
>>> }
>>>
>>> tmp = num_bits;
>>> while(tmp--) {
>>> ocfs2_clear_bit((bit_off + tmp),
>>> (unsigned long *) bg->bg_bitmap);
>>> - if (undo_fn)
>>> + if (undo_fn && undo_bg)
>>> undo_fn(bit_off + tmp,
>>> (unsigned long *) undo_bg->bg_bitmap);
>>> }
>>>
>>
>> .
>>
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