CVE-2024-57929

In the Linux kernel, the following vulnerability has been resolved:

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

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 <KERNEL_DIR>