CVE-2024-57929 dm array: fix releasing a faulty array block twice in dm_array_cursor_end

What is CVE-2024-57929?

CVE-2024-57929 is a high-severity use after free vulnerability in Linux kernel, published on 19 Jan 2025. It can only be exploited from the same machine or local network, with no action from the victim.

Official 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 "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>

Weakness: CWE-672

Which versions are affected by CVE-2024-57929?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2024-57929?

Apply the vendor's patch.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2024-57929 being exploited?

There is no known exploitation of CVE-2024-57929 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BELL-CVE-2024-57929, DEBIAN-CVE-2024-57929, GHSA-q6w5-274c-4fj8, UBUNTU-CVE-2024-57929.