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=$(dd if=/dev/sdc bs=1c count=8 skip=192 2>/dev/null | hexdump -e 1/8 %un) ablock=$(dd if=/dev/sdc bs=1c count=8 skip=$((4096*mapping_root+2056)) 2>/dev/null | hexdump -e 1/8 %un) dd if=/dev/zero of=/dev/sdc bs=4k count=1 seek=$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>

Affected Software

References

• https://git.kernel.org/stable/c/017c4470bff53585370028fec9341247bad358ff
• https://git.kernel.org/stable/c/6002bec5354f86d1a2df21468f68e3ec03ede9da
• https://git.kernel.org/stable/c/738994872d77e189b2d13c501a1d145e95d98f46
• https://git.kernel.org/stable/c/9c7c03d0e926762adf3a3a0ba86156fb5e19538b
• https://git.kernel.org/stable/c/e477021d252c007f0c6d45b5d13d341efed03979
• https://git.kernel.org/stable/c/f2893c0804d86230ffb8f1c8703fdbb18648abc8
• https://git.kernel.org/stable/c/fc1ef07c3522e257e32702954f265debbcb096a7