On 10/24/25 03:15, Nikola Z. Ivanov wrote: > On Wed, Oct 15, 2025 at 03:55:40PM +0300, Nikola Z. Ivanov wrote: >> On Wed, Oct 15, 2025 at 02:41:53PM +0800, Chao Yu wrote: >>> On 10/14/25 20:17, Nikola Z. Ivanov wrote: >>>> On Mon, Oct 13, 2025 at 08:53:04PM +0800, Chao Yu wrote: >>>>> On 10/13/25 05:19, Nikola Z. Ivanov wrote: >>>>>> On Thu, Oct 09, 2025 at 10:54:40AM +0800, Chao Yu wrote: >>>>>>> On 10/3/2025 9:47 PM, Nikola Z. Ivanov wrote: >>>>>>>> Current i_nlink corruption check does not take into account >>>>>>>> directory inodes which have one additional i_nlink for their "." entry. >>>>>>>> >>>>>>>> Add additional check and a common corruption path. >>>>>>>> >>>>>>>> Reported-by: [email protected] >>>>>>>> Closes: https://syzkaller.appspot.com/bug?extid=c07d47c7bc68f47b9083 >>>>>>>> Fixes: 81edb983b3f5 ("f2fs: add check for deleted inode") >>>>>>>> Signed-off-by: Nikola Z. Ivanov <[email protected]> >>>>>>>> --- >>>>>>>> fs/f2fs/namei.c | 28 ++++++++++++++++++++-------- >>>>>>>> 1 file changed, 20 insertions(+), 8 deletions(-) >>>>>>>> >>>>>>>> diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c >>>>>>>> index b882771e4699..68b33e8089b0 100644 >>>>>>>> --- a/fs/f2fs/namei.c >>>>>>>> +++ b/fs/f2fs/namei.c >>>>>>>> @@ -502,12 +502,14 @@ static struct dentry *f2fs_lookup(struct inode >>>>>>>> *dir, struct dentry *dentry, >>>>>>>> goto out; >>>>>>>> } >>>>>>>> - if (inode->i_nlink == 0) { >>>>>>>> + if (unlikely(inode->i_nlink == 0)) { >>>>>>>> f2fs_warn(F2FS_I_SB(inode), "%s: inode (ino=%lx) has >>>>>>>> zero i_nlink", >>>>>>>> __func__, inode->i_ino); >>>>>>>> - err = -EFSCORRUPTED; >>>>>>>> - set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_FSCK); >>>>>>>> - goto out_iput; >>>>>>>> + goto corrupted; >>>>>>>> + } else if (unlikely(S_ISDIR(inode->i_mode) && inode->i_nlink == >>>>>>>> 1)) { >>>>>>>> + f2fs_warn(F2FS_I_SB(inode), "%s: directory inode >>>>>>>> (ino=%lx) has a single i_nlink", >>>>>>>> + __func__, inode->i_ino); >>>>>>>> + goto corrupted; >>>>>>> >>>>>>> Can we detect such corruption in sanity_check_inode() as well? So that >>>>>>> if >>>>>>> f2fs internal flow calls f2fs_iget() on corrupted inode, we can set >>>>>>> SBI_NEED_FSCK >>>>>>> flag and then triggering fsck repairment later. >>>>>>> >>>>>>> Thanks, >>>>>>> >>>>>>>> } >>>>>>>> if (IS_ENCRYPTED(dir) && >>>>>>>> @@ -533,6 +535,9 @@ static struct dentry *f2fs_lookup(struct inode >>>>>>>> *dir, struct dentry *dentry, >>>>>>>> trace_f2fs_lookup_end(dir, !IS_ERR_OR_NULL(new) ? new : dentry, >>>>>>>> ino, IS_ERR(new) ? PTR_ERR(new) : err); >>>>>>>> return new; >>>>>>>> +corrupted: >>>>>>>> + err = -EFSCORRUPTED; >>>>>>>> + set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_FSCK); >>>>>>>> out_iput: >>>>>>>> iput(inode); >>>>>>>> out: >>>>>>>> @@ -572,10 +577,11 @@ static int f2fs_unlink(struct inode *dir, struct >>>>>>>> dentry *dentry) >>>>>>>> if (unlikely(inode->i_nlink == 0)) { >>>>>>>> f2fs_warn(F2FS_I_SB(inode), "%s: inode (ino=%lx) has >>>>>>>> zero i_nlink", >>>>>>>> __func__, inode->i_ino); >>>>>>>> - err = -EFSCORRUPTED; >>>>>>>> - set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_FSCK); >>>>>>>> - f2fs_folio_put(folio, false); >>>>>>>> - goto fail; >>>>>>>> + goto corrupted; >>>>>>>> + } else if (unlikely(S_ISDIR(inode->i_mode) && inode->i_nlink == >>>>>>>> 1)) { >>>>>>>> + f2fs_warn(F2FS_I_SB(inode), "%s: directory inode >>>>>>>> (ino=%lx) has a single i_nlink", >>>>>>>> + __func__, inode->i_ino); >>>>>>>> + goto corrupted; >>>>>>>> } >>>>>>>> f2fs_balance_fs(sbi, true); >>>>>>>> @@ -601,6 +607,12 @@ static int f2fs_unlink(struct inode *dir, struct >>>>>>>> dentry *dentry) >>>>>>>> if (IS_DIRSYNC(dir)) >>>>>>>> f2fs_sync_fs(sbi->sb, 1); >>>>>>>> + >>>>>>>> + goto fail; >>>>>>>> +corrupted: >>>>>>>> + err = -EFSCORRUPTED; >>>>>>>> + set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_FSCK); >>>>>>>> + f2fs_folio_put(folio, false); >>>>>>>> fail: >>>>>>>> trace_f2fs_unlink_exit(inode, err); >>>>>>>> return err; >>>>>>> >>>>>> >>>>>> Hi Chao, >>>>>> >>>>>> Thank you for the suggestion. >>>>>> I will add this to sanity_check_inode and remove it >>>>>> from f2fs_lookup as it becomes redundant since f2fs_lookup >>>>>> obtains the inode through f2fs_iget. For f2fs_unlink I will >>>>>> move the i_nlink == 1 check to f2fs_rmdir. >>>>> >>>>> Hi Nikola, >>>>> >>>>> I meant we can move the i_nlink == 1 check from both f2fs_lookup() and >>>>> f2fs_unlink() to sanity_check_inode(), because before we create in-memory >>>>> inode, we will always call sanity_check_inode(). >>>>> >>>>> Let me know if you have other concerns. >>>>> >>>>> Thanks, >>>>> >>>> >>>> The issue here is that sanity_check_inode will be called only when >>>> we initially read the inode off disk, not when it's already in the cache >>>> >>>> The syzkaller repro does something like this: >>>> Creates a directory structure /dir1/dir2 where dir1 has >>>> i_nlink == 2, which is one less than it should. It then does >>>> rmdir(/dir1/dir2) followed by rmdir(/dir1) which leads to the warning. >>> >>> Oh, I missed this case. >>> >>>> >>>> In such case what would you say should happen, should the second rmdir >>>> fail and report the corruption, or do we close our eyes and just drop >>>> i_nlink to 0 and possibly log a message that something isn't quite right? >>> >>> I agreed that we should keep i_nlink == 1 check in f2fs_unlink(). >>> >>> Thanks, >>> >> >> Hi Chao, >> >> Just to make sure we're on the same page, do you mean to keep the check >> in f2fs_unlink as well as sanity_check_inode, or only do it in f2fs_unlink? >> > > Hello, > > Kindly sending a reminder here, could you please > provide input when you have the chance?
Hi Nikola, Sorry for the delay, I missed to reply. I meant that we can add sanity check (i_nlink == 1) for directory in: - f2fs_unlink(), so that, we can detect runtime i_nlink inconsistency. - sanity_check_inode(), then, we can detect on-disk i_nlink inconsistency. Thanks, > > Thank you! > >>>> >>>> Thank you, >>>> >>>>>> >>>>>> I will send v2 as soon as I do some more testing. >>>>> >>> _______________________________________________ Linux-f2fs-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
