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? 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
