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| author | Shardul Bankar <shardul.b@mpiricsoftware.com> | 2026-03-18 10:38:22 +0300 |
|---|---|---|
| committer | Viacheslav Dubeyko <slava@dubeyko.com> | 2026-03-19 06:48:53 +0300 |
| commit | a8eed0ba6a4b2f1803ecdfa9f11a4818cf87c474 (patch) | |
| tree | 812bec3c41aef80a6548569702ba0d343bd1f6b3 /include | |
| parent | b099ed598c64c8d275fc8877ec521b58712ab103 (diff) | |
| download | linux-a8eed0ba6a4b2f1803ecdfa9f11a4818cf87c474.tar.xz | |
hfsplus: refactor b-tree map page access and add node-type validation
In HFS+ b-trees, the node allocation bitmap is stored across multiple
records. The first chunk resides in the b-tree Header Node at record
index 2, while all subsequent chunks are stored in dedicated Map Nodes
at record index 0.
This structural quirk forces callers like hfs_bmap_alloc() and
hfs_bmap_free() to duplicate boilerplate code to validate offsets, correct
lengths, and map the underlying pages via kmap_local_page(). There is
also currently no strict node-type validation before reading these
records, leaving the allocator vulnerable if a corrupted image points a
map linkage to an Index or Leaf node.
Introduce a unified bit-level API to encapsulate the map record access:
1. A new `struct hfs_bmap_ctx` to cleanly pass state and safely handle
page math across all architectures.
2. `hfs_bmap_get_map_page()`: Automatically validates node types
(HFS_NODE_HEADER vs HFS_NODE_MAP), infers the correct record index,
handles page-boundary math, and returns the unmapped `struct page *`
directly to the caller to avoid asymmetric mappings.
3. `hfs_bmap_clear_bit()`: A clean wrapper that internally handles page
mapping/unmapping for single-bit operations.
Refactor hfs_bmap_alloc() and hfs_bmap_free() to utilize this new API.
This deduplicates the allocator logic, hardens the map traversal against
fuzzed images, and provides the exact abstractions needed for upcoming
mount-time validation checks.
Signed-off-by: Shardul Bankar <shardul.b@mpiricsoftware.com>
Reviewed-by: Viacheslav Dubeyko <slava@dubeyko.com>
Tested-by: Viacheslav Dubeyko <slava@dubeyko.com>
Signed-off-by: Viacheslav Dubeyko <slava@dubeyko.com>
Link: https://lore.kernel.org/r/20260318073823.3933718-2-shardul.b@mpiricsoftware.com
Signed-off-by: Viacheslav Dubeyko <slava@dubeyko.com>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/hfs_common.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/hfs_common.h b/include/linux/hfs_common.h index dadb5e0aa8a3..be24c687858e 100644 --- a/include/linux/hfs_common.h +++ b/include/linux/hfs_common.h @@ -510,6 +510,8 @@ struct hfs_btree_header_rec { #define HFSPLUS_NODE_MXSZ 32768 #define HFSPLUS_ATTR_TREE_NODE_SIZE 8192 #define HFSPLUS_BTREE_HDR_NODE_RECS_COUNT 3 +#define HFSPLUS_BTREE_HDR_MAP_REC_INDEX 2 /* Map (bitmap) record in Header node */ +#define HFSPLUS_BTREE_MAP_NODE_REC_INDEX 0 /* Map record in Map Node */ #define HFSPLUS_BTREE_HDR_USER_BYTES 128 /* btree key type */ |