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ntfs: bound the adjacent cluster in MFT bitmap extension

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When the last MFT bitmap run reaches the volume boundary, the direct
allocation path tests the bit for nr_clusters, an invalid LCN. A clear
bit allows an out-of-volume allocation; a bitmap read failure aborts
extension even if valid clusters remain available.

Check the candidate LCN before accessing $Bitmap and fall back to
ntfs_cluster_alloc() with no locality hint when it is outside the volume.

Reviewed-by: Baolin Liu <liubaolin@kylinos.cn>
Signed-off-by: Xuewen Wang <wangxuewen@kylinos.cn>
Reviewed-by: Baolin Liu <liubaolin@kylinos.cn>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
This commit is contained in:
Xuewen Wang 2026-09-24 09:45:11 +08:00 committed by Namjae Jeon
parent c1bd2f1c22
commit 3f58365687
1 changed files with 6 additions and 0 deletions
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6
fs/ntfs/mft.c
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@ -1377,6 +1377,11 @@ static int ntfs_mft_bitmap_extend_allocation_nolock(struct ntfs_volume *vol)
lcn = rl->lcn + rl->length;
ntfs_debug("Last lcn of mft bitmap attribute is 0x%llx.",
(long long)lcn);
/* There is no adjacent cluster if the last run ends at the volume end. */
if (lcn >= vol->nr_clusters) {
lcn = -1;
goto alloc_cluster;
}
/*
* Attempt to get the cluster following the last allocated cluster by
* hand as it may be in the MFT zone so the allocator would not give it
@ -1413,6 +1418,7 @@ static int ntfs_mft_bitmap_extend_allocation_nolock(struct ntfs_volume *vol)
kunmap_local(b);
folio_put(folio);
up_write(&vol->lcnbmp_lock);
alloc_cluster:
/* Allocate a cluster from the DATA_ZONE. */
rl2 = ntfs_cluster_alloc(vol, rl[1].vcn, 1, lcn, DATA_ZONE,
true, false, false);