Re: [PATCH 3/3] f2fs: fix to do sanity check on i_nid for inline_data inode

Chao Yu
2024-05-11T03:07:21Z

On 2024/5/11 8:38, Jaegeuk Kim wrote:
> On 05/10, Chao Yu wrote:
>> On 2024/5/10 11:36, Jaegeuk Kim wrote:
>>> On 05/10, Chao Yu wrote:
>>>> 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@syzkaller.appspotmail.com
>>>>>> Closes: https://lore.kernel.org/linux-f2fs-devel/000000000000d103ce06174d7ec3@google.com
>>>>>> Signed-off-by: Chao Yu <chao@kernel.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().
>>>
>>> Wasn't detected by sanity_check_inode?
>>
>> I fuzzed non-inline inode w/ below metadata fields:
>> - i_blocks = 1
>> - i_size = 2048
>> - i_inline |= 0x02
>>
>> sanity_check_inode() doesn't complain.
>
> I mean, the below sanity_check_inode() can cover the fuzzed case? I'm wondering

I didn't figure out a generic way in sanity_check_inode() to catch all fuzzed cases.

e.g.
case #1
- blkaddr, its dnode, SSA and SIT are consistent
- dnode.footer.ino points to inline inode
- inline inode doesn't link to the donde

Something like fuzzed special file, please check details in below commit:

9056d6489f5a ("f2fs: fix to do sanity check on inode type during garbage collection")

case #2
- blkaddr, its dnode, SSA and SIT are consistent
- blkaddr locates in inline inode's i_addr

Thanks,

> whether we really need to check it in the gc path.
>
>>
>> Thanks,
>>
>>>
>>>>
>>>> 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