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| author | Bryam Vargas <hexlabsecurity@proton.me> | 2026-07-26 18:29:11 -0500 |
|---|---|---|
| committer | Namjae Jeon <linkinjeon@kernel.org> | 2026-08-19 18:16:45 +0900 |
| commit | 19cac7902a8ab748e15f98ddaafcf5f8882be21d (patch) | |
| tree | 3f530ab202b592322c381a93a8e9e2ce271fd102 | |
| parent | 4d730a4dd78caa7bf29dda36fa5340a0237a8689 (diff) | |
| download | linux-19cac7902a8ab748e15f98ddaafcf5f8882be21d.tar.gz linux-19cac7902a8ab748e15f98ddaafcf5f8882be21d.zip | |
ntfs: bound the free-cluster bitmap scan to the volume
vol->lcn_empty_bits_per_page is sized from vol->nr_clusters at mount, but
ntfs_cluster_alloc() bounds its scan of that array by the size of $Bitmap.
Those are independent on-disk quantities and the mount-time check only
rejects a $Bitmap that is too small, so an image whose $Bitmap covers more
clusters than the volume has lets the scan index past the array. A run
whose LCN lies in that gap takes the allocator straight there, since the
caller passes the file's own last LCN as its locality hint. KASAN reports
a slab out-of-bounds read when a file on such a volume is extended.
Clamp the scan to what that array covers, mirroring the max_index
calculation the mount-time scan already uses, and reject a decoded LCN
at or beyond nr_clusters in the mapping pairs decoder. Conforming
volumes are unaffected.
Fixes: 11ccc9107dc4 ("ntfs: update runlist handling and cluster allocator")
Cc: stable@vger.kernel.org
Signed-off-by: Bryam Vargas <hexlabsecurity@proton.me>
Reviewed-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
| -rw-r--r-- | fs/ntfs/lcnalloc.c | 7 | ||||
| -rw-r--r-- | fs/ntfs/runlist.c | 7 |
2 files changed, 13 insertions, 1 deletions
diff --git a/fs/ntfs/lcnalloc.c b/fs/ntfs/lcnalloc.c index 835a041023a2..aa2e017a4384 100644 --- a/fs/ntfs/lcnalloc.c +++ b/fs/ntfs/lcnalloc.c @@ -298,7 +298,12 @@ struct runlist_element *ntfs_cluster_alloc(struct ntfs_volume *vol, const s64 st clusters = count; rlpos = rlsize = 0; mapping = lcnbmp_vi->i_mapping; - i_size = i_size_read(lcnbmp_vi); + /* + * lcn_empty_bits_per_page is sized from nr_clusters, but $Bitmap can + * cover more clusters than that; bound the scan by the array. + */ + i_size = min_t(s64, i_size_read(lcnbmp_vi), + ((s64)vol->nr_clusters + 7) >> 3); while (1) { ntfs_debug("Start of outer while loop: done_zones 0x%x, search_zone %i, pass %i, zone_start 0x%llx, zone_end 0x%llx, bmp_initial_pos 0x%llx, bmp_pos 0x%llx, rlpos %i, rlsize %i.", done_zones, search_zone, pass, diff --git a/fs/ntfs/runlist.c b/fs/ntfs/runlist.c index 8e0fd400e7f7..17eb275a21ff 100644 --- a/fs/ntfs/runlist.c +++ b/fs/ntfs/runlist.c @@ -884,6 +884,13 @@ struct runlist_element *ntfs_mapping_pairs_decompress(const struct ntfs_volume * ntfs_error(vol->sb, "lcn == -1"); } #endif + /* Check lcn is within the volume. */ + if (unlikely(lcn >= (s64)vol->nr_clusters)) { + ntfs_error(vol->sb, + "LCN >= nr_clusters in mapping pairs array."); + goto err_out; + } + /* Check lcn is not below -1. */ if (unlikely(lcn < -1)) { ntfs_error(vol->sb, "Invalid s64 < -1 in mapping pairs array."); |