CVE-2022-49078

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

lz4: fix LZ4_decompress_safe_partial read out of bound

When partialDecoding, it is EOF if weve either filled the output buffer or cant proceed with reading an offset for following match.

In some extreme corner cases when compressed data is suitably corrupted, UAF will occur. As reported by KASAN [1], LZ4_decompress_safe_partial may lead to read out of bound problem during decoding. lz4 upstream has fixed it [2] and this issue has been disscussed here [3] before.

current decompression routine was ported from lz4 v1.8.3, bumping lib/lz4 to v1.9.+ is certainly a huge work to be done later, so, wed better fix it first.

[1] https://lore.kernel.org/all/000000000000830d1205cf7f0477@google.com/ [2] https://github.com/lz4/lz4/commit/c5d6f8a8be3927c0bec91bcc58667a6cfad244ad# [3] https://lore.kernel.org/all/CC666AE8-4CA4-4951-B6FB-A2EFDE3AC03B@fb.com/

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/467d5e200ab4486b744fe1776154a43d1aa22d4b
• https://git.kernel.org/stable/c/6adc01a7aa37445dafe8846faa0610a86029b253
• https://git.kernel.org/stable/c/73953dfa9d50e5c9fe98ee13fd1d3427aa12a0a3
• https://git.kernel.org/stable/c/9fb8bc6cfc58773ce95414e11c9ccc8fc6ac4927
• https://git.kernel.org/stable/c/e64dbe97c05c769525cbca099ddbd22485630235
• https://git.kernel.org/stable/c/eafc0a02391b7b36617b36c97c4b5d6832cf5e24