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

Chao Yu
2024-05-10T14:16:22Z

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.

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