3.0 KiB
CVE-2024-57929
Description
In the Linux kernel, the following vulnerability has been resolved:dm array: fix releasing a faulty array block twice in dm_array_cursor_endWhen dm_bm_read_lock() fails due to locking or checksum errors, itreleases the faulty block implicitly while leaving an invalid outputpointer behind. The caller of dm_bm_read_lock() should not operate onthis invalid dm_block pointer, or it will lead to undefined result.For example, the dm_array_cursor incorrectly caches the invalid pointeron reading a faulty array block, causing a double release indm_array_cursor_end(), then hitting the BUG_ON in dm-bufio cache_put().Reproduce steps:1. initialize a cache devicedmsetup 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 $262144"dd if=/dev/zero of=/dev/mapper/cmeta bs=4k count=1dmsetup create cache --table "0 524288 cache /dev/mapper/cmeta /dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0"2. wipe the second array block offlinedmsteup remove cache cmeta cdata corigmapping_root=$(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=$ablock3. try reopen the cache devicedmsetup 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 10device-mapper: block manager: array validator check failed for block 10device-mapper: array: get_ablock faileddevice-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 beverified using the "array_cursor/damaged" test in dm-unit: dm-unit run /pdata/array_cursor/damaged --kernel-dir <KERNEL_DIR>
POC
Reference
No PoCs from references.