Re: [PATCH] f2fs: reject invalid recovered filename lengths

[Chao Yu]

On 7/29/26 19:41, Wenjie Qi wrote:
> Recovery uses raw_inode->i_namelen directly when rebuilding fsynced
> dentries. A zero-length name uses no dentry slots, so recovery can
> report success without recreating the dentry.
>
> Treat zero-length and oversized recovered names as corruption, mark
> NEED_FSCK, and stop recovery with -EFSCORRUPTED.

Do you have a reproducer for this? maybe using inject.f2fs? It will be
better to cover those bugs w/ xfsqa testcase, could you please consider
to add it?

> Signed-off-by: Wenjie Qi <qiwenjie@xxxxxxxxxx>
> ---
>   fs/f2fs/recovery.c | 14 +++++++++++---
>   1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
> index 89af8407b667..70cf99efcb3c 100644
> --- a/fs/f2fs/recovery.c
> +++ b/fs/f2fs/recovery.c
> @@ -126,8 +126,8 @@ static int init_recovered_filename(const struct inode *dir,
>   	fname->disk_name.len = le32_to_cpu(raw_inode->i_namelen);
>   	fname->disk_name.name = raw_inode->i_name;
>   
> -	if (WARN_ON(fname->disk_name.len > F2FS_NAME_LEN))
> -		return -ENAMETOOLONG;
> +	if (!fname->disk_name.len || fname->disk_name.len > F2FS_NAME_LEN)

unlikely?

relocate error handling here?

Thanks,

> +		return -EFSCORRUPTED;
>   
>   	if (!IS_ENCRYPTED(dir)) {
>   		usr_fname->name = fname->disk_name.name;
> @@ -185,8 +185,16 @@ static int recover_dentry(struct inode *inode, struct folio *ifolio,
>   
>   	dir = entry->inode;
>   	err = init_recovered_filename(dir, raw_inode, &fname, &usr_fname);
> -	if (err)
> +	if (err) {
> +		if (err == -EFSCORRUPTED) {
> +			f2fs_err(F2FS_I_SB(inode),
> +				 "invalid recovered filename length %u for ino %llu",
> +				 le32_to_cpu(raw_inode->i_namelen), inode->i_ino);
> +			set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_FSCK);
> +			f2fs_handle_error(F2FS_I_SB(inode), ERROR_CORRUPTED_INODE);
> +		}
>   		goto out;
> +	}
>   retry:
>   	de = __f2fs_find_entry(dir, &fname, &folio);
>   	if (de && inode->i_ino == le32_to_cpu(de->ino))