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? > > > > 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
