linux-kernel - Re: [PATCH 3/3] f2fs: fix to do sanity check on i_nid for inline

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Date: Fri, 10 May 2024 10:14:19 +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,
 syzbot+848062ba19c8782ca5c8@...kaller.appspotmail.com
Subject: Re: [PATCH 3/3] f2fs: fix to do sanity check on i_nid for inline_data
 inode

On 2024/5/9 23:52, Jaegeuk Kim wrote:
> On 05/06, Chao Yu wrote:
>> syzbot reports a f2fs bug as below:
>>
>> ------------[ cut here ]------------
>> kernel BUG at fs/f2fs/inline.c:258!
>> CPU: 1 PID: 34 Comm: kworker/u8:2 Not tainted 6.9.0-rc6-syzkaller-00012-g9e4bc4bcae01 #0
>> RIP: 0010:f2fs_write_inline_data+0x781/0x790 fs/f2fs/inline.c:258
>> Call Trace:
>>   f2fs_write_single_data_page+0xb65/0x1d60 fs/f2fs/data.c:2834
>>   f2fs_write_cache_pages fs/f2fs/data.c:3133 [inline]
>>   __f2fs_write_data_pages fs/f2fs/data.c:3288 [inline]
>>   f2fs_write_data_pages+0x1efe/0x3a90 fs/f2fs/data.c:3315
>>   do_writepages+0x35b/0x870 mm/page-writeback.c:2612
>>   __writeback_single_inode+0x165/0x10b0 fs/fs-writeback.c:1650
>>   writeback_sb_inodes+0x905/0x1260 fs/fs-writeback.c:1941
>>   wb_writeback+0x457/0xce0 fs/fs-writeback.c:2117
>>   wb_do_writeback fs/fs-writeback.c:2264 [inline]
>>   wb_workfn+0x410/0x1090 fs/fs-writeback.c:2304
>>   process_one_work kernel/workqueue.c:3254 [inline]
>>   process_scheduled_works+0xa12/0x17c0 kernel/workqueue.c:3335
>>   worker_thread+0x86d/0xd70 kernel/workqueue.c:3416
>>   kthread+0x2f2/0x390 kernel/kthread.c:388
>>   ret_from_fork+0x4d/0x80 arch/x86/kernel/process.c:147
>>   ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
>>
>> The root cause is: inline_data inode can be fuzzed, so that there may
>> be valid blkaddr in its direct node, once f2fs triggers background GC
>> to migrate the block, it will hit f2fs_bug_on() during dirty page
>> writeback.
>>
>> Let's add sanity check on i_nid field for inline_data inode, meanwhile,
>> forbid to migrate inline_data inode's data block to fix this issue.
>>
>> Reported-by: syzbot+848062ba19c8782ca5c8@...kaller.appspotmail.com
>> Closes: https://lore.kernel.org/linux-f2fs-devel/000000000000d103ce06174d7ec3@google.com
>> Signed-off-by: Chao Yu <chao@...nel.org>
>> ---
>>   fs/f2fs/f2fs.h   |  2 +-
>>   fs/f2fs/gc.c     |  6 ++++++
>>   fs/f2fs/inline.c | 17 ++++++++++++++++-
>>   fs/f2fs/inode.c  |  2 +-
>>   4 files changed, 24 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>> index fced2b7652f4..c876813b5532 100644
>> --- a/fs/f2fs/f2fs.h
>> +++ b/fs/f2fs/f2fs.h
>> @@ -4146,7 +4146,7 @@ extern struct kmem_cache *f2fs_inode_entry_slab;
>>    * inline.c
>>    */
>>   bool f2fs_may_inline_data(struct inode *inode);
>> -bool f2fs_sanity_check_inline_data(struct inode *inode);
>> +bool f2fs_sanity_check_inline_data(struct inode *inode, struct page *ipage);
>>   bool f2fs_may_inline_dentry(struct inode *inode);
>>   void f2fs_do_read_inline_data(struct page *page, struct page *ipage);
>>   void f2fs_truncate_inline_inode(struct inode *inode,
>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>> index e86c7f01539a..041957750478 100644
>> --- a/fs/f2fs/gc.c
>> +++ b/fs/f2fs/gc.c
>> @@ -1563,6 +1563,12 @@ static int gc_data_segment(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>>   				continue;
>>   			}
>>   
>> +			if (f2fs_has_inline_data(inode)) {
>> +				iput(inode);
>> +				set_sbi_flag(sbi, SBI_NEED_FSCK);
>> +				continue;
> 
> Any race condtion to get this as false alarm?

Since there is no reproducer for the bug, I doubt it was caused by metadata
fuzzing, something like this:

- inline inode has one valid blkaddr in i_addr or in dnode reference by i_nid;
- SIT/SSA entry of the block is valid;
- background GC migrates the block;
- kworker writeback it, and trigger the bug_on().

Thoughts?

Thanks,

> 
>> +			}
>> +
>>   			err = f2fs_gc_pinned_control(inode, gc_type, segno);
>>   			if (err == -EAGAIN) {
>>   				iput(inode);
>> diff --git a/fs/f2fs/inline.c b/fs/f2fs/inline.c
>> index ac00423f117b..067600fed3d4 100644
>> --- a/fs/f2fs/inline.c
>> +++ b/fs/f2fs/inline.c
>> @@ -33,11 +33,26 @@ bool f2fs_may_inline_data(struct inode *inode)
>>   	return !f2fs_post_read_required(inode);
>>   }
>>   
>> -bool f2fs_sanity_check_inline_data(struct inode *inode)
>> +static bool has_node_blocks(struct inode *inode, struct page *ipage)
>> +{
>> +	struct f2fs_inode *ri = F2FS_INODE(ipage);
>> +	int i;
>> +
>> +	for (i = 0; i < DEF_NIDS_PER_INODE; i++) {
>> +		if (ri->i_nid[i])
>> +			return true;
>> +	}
>> +	return false;
>> +}
>> +
>> +bool f2fs_sanity_check_inline_data(struct inode *inode, struct page *ipage)
>>   {
>>   	if (!f2fs_has_inline_data(inode))
>>   		return false;
>>   
>> +	if (has_node_blocks(inode, ipage))
>> +		return false;
>> +
>>   	if (!support_inline_data(inode))
>>   		return true;
>>   
>> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
>> index c26effdce9aa..1423cd27a477 100644
>> --- a/fs/f2fs/inode.c
>> +++ b/fs/f2fs/inode.c
>> @@ -343,7 +343,7 @@ static bool sanity_check_inode(struct inode *inode, struct page *node_page)
>>   		}
>>   	}
>>   
>> -	if (f2fs_sanity_check_inline_data(inode)) {
>> +	if (f2fs_sanity_check_inline_data(inode, node_page)) {
>>   		f2fs_warn(sbi, "%s: inode (ino=%lx, mode=%u) should not have inline_data, run fsck to fix",
>>   			  __func__, inode->i_ino, inode->i_mode);
>>   		return false;
>> -- 
>> 2.40.1