kernel/linux.git/drivers/md/persistent-data/dm-array.c, branch v7.3-rc1

dm array: reject an array block whose value size is not the caller's

2026-08-04T08:19:29+00:00

array_block_check() can only compare the header against itself, so a block with value_size 4 and max_entries 1018 is internally consistent and passes. dm-cache keeps two arrays -- mappings at 8 bytes and hints at 4 -- and the roots for both live in the superblock. Point the mappings root at a hint block and __load_mappings() walks it through an info whose value size is 8, so element_at() strides 8 bytes over 4-byte entries and reaches offset 8160 of a 4096-byte block. get_ablock() and __shadow_ablock() are the two places that hold the block and the caller at once. Reject there when the two value sizes disagree. Arrays only ever read their own blocks, so this fires on crafted metadata only. Fixes: 6513c29f44f2 ("dm persistent data: add transactional array") Suggested-by: Ming-Hung Tsai Cc: stable@vger.kernel.org Signed-off-by: Bryam Vargas Reviewed-by: Ming-Hung Tsai Signed-off-by: Mikulas Patocka

dm array: validate array block headers on read

2026-08-04T08:19:19+00:00

array_block_check() validates blocknr and csum and nothing else, while node_check(), next to it, has bounded the structural fields since both were written. dm_array_cursor_next() takes its loop bound from the on-disk nr_entries and element_at() is unguarded pointer arithmetic, so a count larger than the block holds keeps the cursor in one block while the index grows past it and the read walks off the dm-bufio buffer -- dm_cache_load_mappings() drives it once per cache block at activation. Check the header against itself: reject a zero value_size, require max_entries to equal calc_max_entries() for that value_size and block size, and require nr_entries to fit. Equality rather than an upper bound, since a count below the real capacity trips BUG_ON() in fill_ablock() and trim_ablock(). Metadata dm-array writes satisfies all three. Fixes: 6513c29f44f2 ("dm persistent data: add transactional array") Suggested-by: Ming-Hung Tsai Cc: stable@vger.kernel.org Signed-off-by: Bryam Vargas Reviewed-by: Ming-Hung Tsai Signed-off-by: Mikulas Patocka

dm array: fix cursor index when skipping across block boundaries

2024-12-13T13:39:18+00:00

dm_array_cursor_skip() seeks to the target position by loading array blocks iteratively until the specified number of entries to skip is reached. When seeking across block boundaries, it uses dm_array_cursor_next() to step into the next block. dm_array_cursor_skip() must first move the cursor index to the end of the current block; otherwise, the cursor position could incorrectly remain in the same block, causing the actual number of skipped entries to be much smaller than expected. This bug affects cache resizing in v2 metadata and could lead to data loss if the fast device is shrunk during the first-time resume. For example: 1. create a cache metadata consists of 32768 blocks, with a dirty block assigned to the second bitmap block. cache_restore v1.0 is required. cat <> cmeta.xml EOF dmsetup create cmeta --table "0 8192 linear /dev/sdc 0" cache_restore -i cmeta.xml -o /dev/mapper/cmeta --metadata-version=2 2. bring up the cache while attempt to discard all the blocks belonging to the second bitmap block (block# 32576 to 32767). The last command is expected to fail, but it actually succeeds. dmsetup create cdata --table "0 2084864 linear /dev/sdc 8192" dmsetup create corig --table "0 65536 linear /dev/sdc 2105344" dmsetup create cache --table "0 65536 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 64 2 metadata2 writeback smq \ 2 migration_threshold 0" In addition to the reproducer described above, this fix can be verified using the "array_cursor/skip" tests in dm-unit: dm-unit run /pdata/array_cursor/skip/ --kernel-dir Signed-off-by: Ming-Hung Tsai Fixes: 9b696229aa7d ("dm persistent data: add cursor skip functions to the cursor APIs") Reviewed-by: Joe Thornber Signed-off-by: Mike Snitzer

dm array: fix unreleased btree blocks on closing a faulty array cursor

2024-12-13T13:37:39+00:00

The cached block pointer in dm_array_cursor might be NULL if it reaches an unreadable array block, or the array is empty. Therefore, dm_array_cursor_end() should call dm_btree_cursor_end() unconditionally, to prevent leaving unreleased btree blocks. This fix can be verified using the "array_cursor/iterate/empty" test in dm-unit: dm-unit run /pdata/array_cursor/iterate/empty --kernel-dir Signed-off-by: Ming-Hung Tsai Fixes: fdd1315aa5f0 ("dm array: introduce cursor api") Reviewed-by: Joe Thornber Signed-off-by: Mike Snitzer

dm array: fix releasing a faulty array block twice in dm_array_cursor_end

2024-12-13T13:33:38+00:00

When dm_bm_read_lock() fails due to locking or checksum errors, it releases the faulty block implicitly while leaving an invalid output pointer behind. The caller of dm_bm_read_lock() should not operate on this invalid dm_block pointer, or it will lead to undefined result. For example, the dm_array_cursor incorrectly caches the invalid pointer on reading a faulty array block, causing a double release in dm_array_cursor_end(), then hitting the BUG_ON in dm-bufio cache_put(). Reproduce steps: 1. initialize a cache device dmsetup create cmeta --table "0 8192 linear /dev/sdc 0" dmsetup create cdata --table "0 65536 linear /dev/sdc 8192" dmsetup create corig --table "0 524288 linear /dev/sdc $262144" dd if=/dev/zero of=/dev/mapper/cmeta bs=4k count=1 dmsetup create cache --table "0 524288 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0" 2. wipe the second array block offline dmsteup remove cache cmeta cdata corig mapping_root=$(dd if=/dev/sdc bs=1c count=8 skip=192 \ 2>/dev/null | hexdump -e '1/8 "%u\n"') ablock=$(dd if=/dev/sdc bs=1c count=8 skip=$((4096*mapping_root+2056)) \ 2>/dev/null | hexdump -e '1/8 "%u\n"') dd if=/dev/zero of=/dev/sdc bs=4k count=1 seek=$ablock 3. try reopen the cache device dmsetup create cmeta --table "0 8192 linear /dev/sdc 0" dmsetup create cdata --table "0 65536 linear /dev/sdc 8192" dmsetup create corig --table "0 524288 linear /dev/sdc $262144" dmsetup create cache --table "0 524288 cache /dev/mapper/cmeta \ /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0" Kernel logs: (snip) device-mapper: array: array_block_check failed: blocknr 0 != wanted 10 device-mapper: block manager: array validator check failed for block 10 device-mapper: array: get_ablock failed device-mapper: cache metadata: dm_array_cursor_next for mapping failed ------------[ cut here ]------------ kernel BUG at drivers/md/dm-bufio.c:638! Fix by setting the cached block pointer to NULL on errors. In addition to the reproducer described above, this fix can be verified using the "array_cursor/damaged" test in dm-unit: dm-unit run /pdata/array_cursor/damaged --kernel-dir Signed-off-by: Ming-Hung Tsai Fixes: fdd1315aa5f0 ("dm array: introduce cursor api") Reviewed-by: Joe Thornber Signed-off-by: Mike Snitzer

dm: Constify struct dm_block_validator

2024-07-19T10:08:15+00:00

'struct dm_block_validator' are not modified in these drivers. Constifying this structure moves some data to a read-only section, so increase overall security. On a x86_64, with allmodconfig, as an example: Before: ====== text data bss dec hex filename 32047 920 16 32983 80d7 drivers/md/dm-cache-metadata.o After: ===== text data bss dec hex filename 32075 896 16 32987 80db drivers/md/dm-cache-metadata.o Signed-off-by: Christophe JAILLET Signed-off-by: Mikulas Patocka

dm: add missing blank line after declarations/fix those

2023-02-14T19:23:07+00:00

Signed-off-by: Heinz Mauelshagen Signed-off-by: Mike Snitzer

dm: prefer '"%s...", func'

2023-02-14T19:23:07+00:00

Signed-off-by: Heinz Mauelshagen Signed-off-by: Mike Snitzer

dm: add missing empty lines

2023-02-14T19:23:06+00:00

Signed-off-by: Heinz Mauelshagen Signed-off-by: Mike Snitzer

dm: change "unsigned" to "unsigned int"

2023-02-14T19:23:06+00:00

Signed-off-by: Heinz Mauelshagen Signed-off-by: Mike Snitzer

kernel/linux.git/drivers/md/persistent-data/dm-array.c, branch v7.3-rc1

dm array: reject an array block whose value size is not the caller's

dm array: validate array block headers on read

dm array: fix cursor index when skipping across block boundaries

dm array: fix unreleased btree blocks on closing a faulty array cursor

dm array: fix releasing a faulty array block twice in dm_array_cursor_end

dm: Constify struct dm_block_validator

dm: add missing blank line after declarations/fix those

dm: prefer '"%s...", __func__'

dm: add missing empty lines

dm: change "unsigned" to "unsigned int"

dm: prefer '"%s...", func'