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

Chao Yu
2024-05-15T06:12:13Z

On 2024/5/15 12:39, Jaegeuk Kim wrote:
> On 05/15, Chao Yu wrote:
>> On 2024/5/15 0:07, Jaegeuk Kim wrote:
>>> 外部邮件/External Mail
>>>
>>>
>>> On 05/11, Chao Yu wrote:
>>>> 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.
>>>
>>>
>>> The patch described:
>>> "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."
>>>
>>> Do you suspect the node block address was suddenly assigned after f2fs_iget()?
>>
>> No, I suspect that the image was fuzzed by tools offline, not in runtime after
>> mount().
>>
>>> Otherwise, it looks checking them in sanity_check_inode would be enough.
>>>
>>>>
>>>> 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
>>
>> The image status is something like above as I described.
>
> Then, why not just checking the gc path only?

Yes, we can.

has_node_blocks() is added for using a quick check to see whether i_nid
and inline_data flag are inconsistent, should we change this in a separated
patch?

Thanks,

>
>>
>> Thanks,
>>
>>>>
>>>> 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