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

Chao Yu
2024-05-10T02:14:22Z

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().

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