Re: [PATCH v3 0/6] ntfs: fix the $MFT bootstrap hang and reads of unmapped runlist ranges

[Namjae Jeon]

On Wed, Sep 30, 2026 at 12:48 PM Matthias Goergens
<matthias.goergens@xxxxxxxxx> wrote:
>
> Hi Hyunchul,
>
> This is v3, with your review of v2 and Baolin's applied:
>
> - Patch 1: a failed retry for a vcn at or beyond allocated_size returns
>   the runlist end again, as in ntfs-next; only lookups below it fail
>   with -EIO.  On its own, v2's patch 1 also failed lookups past EOF,
>   for instance when reading a file's last folio with 512-byte clusters
>   (Baolin).  Baolin suggested moving patch 4's allocated_size check
>   before the retry instead, but that skips a retry ntfs-next makes: on
>   a corrupt volume whose allocated_size is cut to where a file's last
>   extent record starts, the rest of the file was then read as zeros,
>   where ntfs-next and v3's patch 1 read the data (with the whole series,
>   patch 6 rejects that file).
> - Patch 4: the if statement you asked me to merge is gone, as the
>   allocated_size check now sits in patch 1, and in
>   ntfs_attr_vcn_to_rl() patch 4 only extends patch 1's -EIO to
>   LCN_ENOENT.  The expansion rollback restores allocated_size under
>   size_lock.
> - Patch 6: the comment is gone, and $MFT's own non-resident attribute
>   list is checked too (Baolin); a volume where that list claims more
>   data than its allocation used to mount and now fails to.
>
> Patches 2, 3 and 5 are unchanged.
>
> The series fixes a hang at mount when $MFT needs its own extent records
> (patch 3, which needs patch 1).  Patches 1 and 2 fix reads and writes
> of a runlist range held in an extent record that cannot be read, which
> returned zeros with no error or silently lost buffered writes, and
> patch 4 does the same for a runlist that ends before allocated_size.
> Patches 5 and 6 check the sizes of $MFT's data and of every non-resident
> attribute against their allocation, as fs/ntfs3 does.
>
> Tested under qemu with KASAN and the hung-task detector on ntfs-next,
> with and without the series.  Nine crafted images that hang or crash
> the mount without it fail to mount with it, and six that read zeros
> that are not on disk return errors instead.  Eighteen images that mount
> without the series, among them eight public test volumes written by
> Windows or mkntfs, read every file the same with it, and six small
> mkntfs images still mount.  v3 gives the same results as v2 on all of
> them.  The images and the scripts that generate them are at
>
>   https://github.com/matthiasgoergens/linux/tree/reproducer/2026-09-26-ntfs-mft-runlist
>
> and, for the ordinary file of patch 4, the unaligned allocated_size of
> patch 6 and three of the eighteen volumes that mount, at
>
>   https://github.com/matthiasgoergens/linux/tree/reproducer/2026-09-26-ntfs-v2-extra
>
> and, for v3's changes, at
>
>   https://github.com/matthiasgoergens/linux/tree/reproducer/2026-09-30-ntfs-v3
>
> v2: https://lore.kernel.org/all/cover.1790417653.git.matthias.goergens@xxxxxxxxx/
> v1: https://lore.kernel.org/all/20260922153931.1976405-1-matthias.goergens@xxxxxxxxx/
>
> Thanks,
> Matthias
>
> Matthias Goergens (6):
>   ntfs: do not map an unmappable runlist fragment as a hole
>   ntfs: do not turn an unmappable runlist fragment into delalloc on
>     write
>   ntfs: fail the mount when $MFT needs its own extent records
>   ntfs: do not map a vcn as a hole when its runlist lookup failed
>   ntfs: fail the mount when $MFT's data size exceeds its allocation
>   ntfs: reject non-resident attributes whose sizes exceed their
>     allocation
Applied them to #ntfs-next.
Thanks!