On Mon, Nov 03, 2025 at 10:35:17AM +0800, Chao Yu wrote:
> On 11/1/25 20:56, Nikola Z. Ivanov wrote:
> > Add check for inode->i_nlink == 1 for directories during unlink,
> > as their value is decremented twice, which can trigger a warning in
> > drop_nlink. In such case mark the filesystem as corrupted and return
> > from the function call with the relevant failure return value.
> >
> > Additionally add the 2 checks for i_nlink == 0 and i_nlink == 1 in
> > sanity_check_inode in order to detect on-disk corruption early.
> >
> > Reported-by: [email protected]
> > Closes: https://syzkaller.appspot.com/bug?extid=c07d47c7bc68f47b9083
> > Tested-by: [email protected]
> > Signed-off-by: Nikola Z. Ivanov <[email protected]>
> > ---
> > fs/f2fs/inode.c | 10 ++++++++++
> > fs/f2fs/namei.c | 15 +++++++++++----
> > 2 files changed, 21 insertions(+), 4 deletions(-)
> >
> > diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
> > index 8c4eafe9ffac..089cbf3646f0 100644
> > --- a/fs/f2fs/inode.c
> > +++ b/fs/f2fs/inode.c
> > @@ -294,6 +294,16 @@ static bool sanity_check_inode(struct inode *inode,
> > struct folio *node_folio)
> > return false;
> > }
> >
> > + if (unlikely(inode->i_nlink == 0)) {
>
> This is a possible case, as an orphan inode may exist in filesystem after
> sudden
> power-cut.
>
> Thanks,
>
Hi Chao,
Do you suggest that it should not be wrapped in unlikely()?
I also now realise that I intended to wrap the "else if" case
as well but I've missed it in the final patch.
Should I resend the patch with both cases wrapped in "unlikely()"
or would you suggest otherwise?
> > + f2fs_warn(F2FS_I_SB(inode), "%s: inode (ino=%lx) has zero
> > i_nlink",
> > + __func__, inode->i_ino);
> > + return false;
> > + } else if (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);
> > + return false;
> > + }
> > +
> > if (f2fs_has_extra_attr(inode)) {
> > if (!f2fs_sb_has_extra_attr(sbi)) {
> > f2fs_warn(sbi, "%s: inode (ino=%lx) is with extra_attr,
> > but extra_attr feature is off",
> > diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
> > index 40cf80fd9d9a..d13077bad482 100644
> > --- a/fs/f2fs/namei.c
> > +++ b/fs/f2fs/namei.c
> > @@ -572,10 +572,11 @@ 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 out;
> > + goto corrupted;
> > + } else if (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 +602,12 @@ static int f2fs_unlink(struct inode *dir, struct
> > dentry *dentry)
> >
> > if (IS_DIRSYNC(dir))
> > f2fs_sync_fs(sbi->sb, 1);
> > +
> > + goto out;
> > +corrupted:
> > + err = -EFSCORRUPTED;
> > + set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_FSCK);
> > + f2fs_folio_put(folio, false);
> > out:
> > trace_f2fs_unlink_exit(inode, err);
> > return err;
>
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