Re: [PATCH v3 2/2] f2fs: Add sanity checks before unlinking and loading inodes

Chao Yu
2025-11-05T07:27:55Z

On 11/4/25 16:46, 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 check for i_nlink == 1 in
> sanity_check_inode in order to detect on-disk corruption early.
>

Cc: stable@kernel.org

> Reported-by: syzbot+c07d47c7bc68f47b9083@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=c07d47c7bc68f47b9083
> Tested-by: syzbot+c07d47c7bc68f47b9083@syzkaller.appspotmail.com
> Signed-off-by: Nikola Z. Ivanov <zlatistiv@gmail.com>
> ---
> fs/f2fs/inode.c | 6 ++++++
> fs/f2fs/namei.c | 15 +++++++++++----
> 2 files changed, 17 insertions(+), 4 deletions(-)
>
> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
> index 8c4eafe9ffac..b808e1dc2ae7 100644
> --- a/fs/f2fs/inode.c
> +++ b/fs/f2fs/inode.c
> @@ -294,6 +294,12 @@ static bool sanity_check_inode(struct inode *inode, struct folio *node_folio)
> return false;
> }
>
> + if (S_ISDIR(inode->i_mode) && unlikely(inode->i_nlink == 1)) {
> + f2fs_warn(F2FS_I_SB(inode), "%s: directory inode (ino=%lx) has a single i_nlink",

s/F2FS_I_SB(inode)/sbi

> + __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..65af1d56a99e 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) && unlikely(inode->i_nlink == 1)) {
> + f2fs_warn(F2FS_I_SB(inode), "%s: directory inode (ino=%lx) has a single i_nlink",

Ditto,

> + __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);

Ditto,

Thanks,

> + f2fs_folio_put(folio, false);
> out:
> trace_f2fs_unlink_exit(inode, err);
> return err;