linux-kernel - Re: [PATCH] f2fs: fix to detect obsolete inner inode during fill

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Message-ID: <c29df38b-18d7-506b-59a1-d471f2769667@kernel.org>
Date:   Wed, 14 Sep 2022 23:53:50 +0800
From:   Chao Yu <chao@...nel.org>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        syzbot+775a3440817f74fddb8c@...kaller.appspotmail.com
Subject: Re: [PATCH] f2fs: fix to detect obsolete inner inode during
 fill_super()

On 2022/9/13 14:04, Jaegeuk Kim wrote:
> On 09/13, Chao Yu wrote:
>> 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@...r.kernel.org
>>>> Reported-by: syzbot+775a3440817f74fddb8c@...kaller.appspotmail.com
>>>> Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
>>>> Signed-off-by: Chao Yu <chao@...nel.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.
> 
> I don't feel this is a right way to deal with that. If we think it'd be worth
> checking any stale inode object during f2fs_fill_super, we'd better check any
> cached inode given superblock pointer rather than our inner inodes only.

Well, something like this?

f2fs_fill_super()

	for (ino = root_ino; ino < max_nid; ino++) {
		inode = iget_locked(sb, ino);
		if (!inode)
			continue;
		iput(inode);
		ret = -EFSCORRUPTED;
		goto error_handling;
	}

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