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Message-ID: <a03417f6-e4fa-2b1a-34f8-bd5d52c1e853@kernel.org>
Date:   Tue, 13 Sep 2022 10:33:29 +0800
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Subject: Re: [PATCH] f2fs: fix to detect obsolete inner inode during
 fill_super()
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To:     Jaegeuk Kim <jaegeuk@kernel.org>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, stable@vger.kernel.org,
        syzbot+775a3440817f74fddb8c@syzkaller.appspotmail.com
References: <20220908105334.98572-1-chao@kernel.org>
 <Yx9SVsxVzNErMDpv@google.com>
From:   Chao Yu <chao@kernel.org>
In-Reply-To: <Yx9SVsxVzNErMDpv@google.com>
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On 2022/9/12 23:37, Jaegeuk Kim wrote:
> On 09/08, Chao Yu wrote:
>> Sometimes we can get a cached meta_inode which has no aops yet. Let's set it
>> all the time to fix the below panic.
>>
>> Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
>> Mem abort info:
>>    ESR = 0x0000000086000004
>>    EC = 0x21: IABT (current EL), IL = 32 bits
>>    SET = 0, FnV = 0
>>    EA = 0, S1PTW = 0
>>    FSC = 0x04: level 0 translation fault
>> user pgtable: 4k pages, 48-bit VAs, pgdp=0000000109ee4000
>> [0000000000000000] pgd=0000000000000000, p4d=0000000000000000
>> Internal error: Oops: 86000004 [#1] PREEMPT SMP
>> Modules linked in:
>> CPU: 1 PID: 3045 Comm: syz-executor330 Not tainted 6.0.0-rc2-syzkaller-16455-ga41a877bc12d #0
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
>> pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>> pc : 0x0
>> lr : folio_mark_dirty+0xbc/0x208 mm/page-writeback.c:2748
>> sp : ffff800012783970
>> x29: ffff800012783970 x28: 0000000000000000 x27: ffff800012783b08
>> x26: 0000000000000001 x25: 0000000000000400 x24: 0000000000000001
>> x23: ffff0000c736e000 x22: 0000000000000045 x21: 05ffc00000000015
>> x20: ffff0000ca7403b8 x19: fffffc00032ec600 x18: 0000000000000181
>> x17: ffff80000c04d6bc x16: ffff80000dbb8658 x15: 0000000000000000
>> x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
>> x11: ff808000083e9814 x10: 0000000000000000 x9 : ffff8000083e9814
>> x8 : 0000000000000000 x7 : 0000000000000000 x6 : 0000000000000000
>> x5 : ffff0000cbb19000 x4 : ffff0000cb3d2000 x3 : ffff0000cbb18f80
>> x2 : fffffffffffffff0 x1 : fffffc00032ec600 x0 : ffff0000ca7403b8
>> Call trace:
>>   0x0
>>   set_page_dirty+0x38/0xbc mm/folio-compat.c:62
>>   f2fs_update_meta_page+0x80/0xa8 fs/f2fs/segment.c:2369
>>   do_checkpoint+0x794/0xea8 fs/f2fs/checkpoint.c:1522
>>   f2fs_write_checkpoint+0x3b8/0x568 fs/f2fs/checkpoint.c:1679
>>
>> The root cause is, quoted from Jaegeuk:
>>
>> It turned out there is a bug in reiserfs which doesn't free the root
>> inode (ino=2). That leads f2fs to find an ino=2 with the previous
>> superblock point used by reiserfs. That stale inode has no valid
>> mapping that f2fs can use, result in kernel panic.
>>
>> This patch adds sanity check in f2fs_iget() to avoid finding stale
>> inode during inner inode initialization.
>>
>> Cc: stable@vger.kernel.org
>> Reported-by: syzbot+775a3440817f74fddb8c@syzkaller.appspotmail.com
>> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
>> Signed-off-by: Chao Yu <chao@kernel.org>
>> ---
>>   fs/f2fs/inode.c | 11 +++++++++++
>>   1 file changed, 11 insertions(+)
>>
>> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
>> index ccb29034af59..df1a82fbfaf2 100644
>> --- a/fs/f2fs/inode.c
>> +++ b/fs/f2fs/inode.c
>> @@ -493,6 +493,17 @@ struct inode *f2fs_iget_inner(struct super_block *sb, unsigned long ino)
>>   	struct inode *inode;
>>   	int ret = 0;
>>   
>> +	if (ino == F2FS_NODE_INO(sbi) || ino == F2FS_META_INO(sbi) ||
>> +					ino == F2FS_COMPRESS_INO(sbi)) {
>> +		inode = ilookup(sb, ino);
>> +		if (inode) {
>> +			iput(inode);
>> +			f2fs_err(sbi, "there is obsoleted inner inode %lu cached in hash table",
>> +					ino);
>> +			return ERR_PTR(-EFSCORRUPTED);
> 
> Well, this does not indicate f2fs is corrupted. I'd rather expect to fix
> reiserfs instead of f2fs workaround which hides the bug.

Well, is there a fixing patch for reiserfs? If not, how about applying this
patch first, later, we can revert it after reiserfs has been fixed.

Thanks,

> 
>> +		}
>> +	}
>> +
>>   	inode = iget_locked(sb, ino);
>>   	if (!inode)
>>   		return ERR_PTR(-ENOMEM);
>> -- 
>> 2.25.1