CVE-2024-57929 Information

Description

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 �8192 linear /dev/sdc 0\ndmsetup create cdata –table 5536 linear /dev/sdc 8192\ndmsetup create corig –table *4288 linear /dev/sdc $262144\ndd if=/dev/zero of=/dev/mapper/cmeta bs=4k count=1 dmsetup create cache –table *4288 cache /dev/mapper/cmeta
/dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0\n 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=$((4096mapping_root+2056))
2>/dev/null | hexdump -e ‘1/8 %u\n') dd if=/dev/zero of=/dev/sdc bs=4k count=1 seek=$ablock

3. try reopen the cache device

dmsetup create cmeta –table �8192 linear /dev/sdc 0\ndmsetup create cdata –table 5536 linear /dev/sdc 8192\ndmsetup create corig –table *4288 linear /dev/sdc $262144\ndmsetup create cache –table *4288 cache /dev/mapper/cmeta
/dev/mapper/cdata /dev/mapper/corig 128 2 metadata2 writethrough smq 0\n 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 rray_cursor/damaged\ test in dm-unit: dm-unit run /pdata/array_cursor/damaged –kernel-dir <KERNEL_DIR>

Reference

https://git.kernel.org/stable/c/017c4470bff53585370028fec9341247bad358ff https://git.kernel.org/stable/c/6002bec5354f86d1a2df21468f68e3ec03ede9da https://git.kernel.org/stable/c/e477021d252c007f0c6d45b5d13d341efed03979 https://git.kernel.org/stable/c/f2893c0804d86230ffb8f1c8703fdbb18648abc8