CVE-2024-50280

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

dm cache: fix flushing uninitialized delayed_work on cache_ctr error

An unexpected WARN_ON from flush_work() may occur when cache creation fails, caused by destroying the uninitialized delayed_work waker in the error path of cache_create(). For example, the warning appears on the superblock checksum error.

Reproduce steps:

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/urandom of=/dev/mapper/cmeta bs=4k count=1 oflag=direct 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) WARNING: CPU: 0 PID: 84 at kernel/workqueue.c:4178 __flush_work+0x5d4/0x890

Fix by pulling out the cancel_delayed_work_sync() from the constructors error path. This patch doesnt affect the use-after-free fix for concurrent dm_resume and dm_destroy (commit 6a459d8edbdb (dm cache: Fix UAF in destroy())) as cache_dtr is not changed.

Weakness

Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.

Affected Software

Extended Description

The use of previously-freed memory can have any number of adverse consequences, ranging from the corruption of valid data to the execution of arbitrary code, depending on the instantiation and timing of the flaw. The simplest way data corruption may occur involves the system’s reuse of the freed memory. Use-after-free errors have two common and sometimes overlapping causes:

In this scenario, the memory in question is allocated to another pointer validly at some point after it has been freed. The original pointer to the freed memory is used again and points to somewhere within the new allocation. As the data is changed, it corrupts the validly used memory; this induces undefined behavior in the process. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.

Potential Mitigations

References

• https://git.kernel.org/stable/c/135496c208ba26fd68cdef10b64ed7a91ac9a7ff
• https://git.kernel.org/stable/c/5a754d3c771280f2d06bf8ab716d6a0d36ca256e
• https://git.kernel.org/stable/c/8cc12dab635333c4ea28e72d7b947be7d0543c2c
• https://git.kernel.org/stable/c/aee3ecda73ce13af7c3e556383342b57e6bd0718