Re: [PATCH] ntfs: Validate error in ntfs_lookup()

[Hongling Zeng <zhongling0719@126.com>]

   Hi, DaeMyung.
   Thank you for the detailed review. You are absolutely right.

   After looking at the code more carefully, I agree that:
   1. ntfs_lookup_inode_by_name() already normalizes zero err to -EIO
      before ERR_MREF(err), so MREF_ERR(mref) will never be 0 here.
   2. Even if it were 0, returning NULL would be incorrect since this
      is an error path.

   The correct fix would be:
       int err = MREF_ERR(mref);
       return ERR_PTR(err ?: -EIO);

   This ensures we return a proper error code instead of masking
   the bug as success.
   Should I submit a new version with this fix, or just drop this
   patch entirely since the issue doesn't actually exist in practice?

   Thanks for catching this.
   Best regards,
Hongling


在 2026年05月20日 23:10, CharSyam 写道:
> Hi, Hongling.
>
>   I don't think returning NULL is the right fallback here. This branch is
> already the IS_ERR_MREF(mref) path, and -ENOENT has been handled above as
> the negative-dentry case. If MREF_ERR(mref) ever decodes to 0 here, it
> should probably remain an error, e.g. -EIO, rather than being converted
> to a successful lookup return.
>
>    Also, I do not see a current producer for MREF_ERR(mref) == 0:
> ntfs_lookup_inode_by_name() normalizes zero err to -EIO before
> ERR_MREF(err).
>
> The Fixes tag also seems wrong, since the same return is
> already present in af0db57d4293^.
>
> Thanks.
> DaeMyung.
>
> 2026년 5월 20일 (수) 오후 8:16, Hongling Zeng <zenghongling@kylinos.cn>님이 작성:
>> Check that MREF_ERR returns non-zero before using as error pointer.
>> This prevents potential ERR_PTR(0) when error code is zero
>>
>> Fixes: af0db57d4293 ("ntfs: update inode operations")
>> Signed-off-by: Hongling Zeng <zenghongling@kylinos.cn>
>> ---
>>   fs/ntfs/namei.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/ntfs/namei.c b/fs/ntfs/namei.c
>> index 10894de519c3..bb075aa97b53 100644
>> --- a/fs/ntfs/namei.c
>> +++ b/fs/ntfs/namei.c
>> @@ -236,7 +236,7 @@ static struct dentry *ntfs_lookup(struct inode *dir_ino, struct dentry *dent,
>>          }
>>          ntfs_error(vol->sb, "ntfs_lookup_ino_by_name() failed with error code %i.",
>>                          -MREF_ERR(mref));
>> -       return ERR_PTR(MREF_ERR(mref));
>> +       return MREF_ERR(mref) ? ERR_PTR(MREF_ERR(mref)) : NULL;
>>   handle_name:
>>          {
>>                  struct mft_record *m;
>> --
>> 2.25.1
>>
>>