CVE-2022-49291

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

ALSA: pcm: Fix races among concurrent hw_params and hw_free calls

Currently we have neither proper check nor protection against the concurrent calls of PCM hw_params and hw_free ioctls, which may result in a UAF. Since the existing PCM stream lock cant be used for protecting the whole ioctl operations, we need a new mutex to protect those racy calls.

This patch introduced a new mutex, runtime->buffer_mutex, and applies it to both hw_params and hw_free ioctl code paths. Along with it, the both functions are slightly modified (the mmap_count check is moved into the state-check block) for code simplicity.

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/0090c13cbbdffd7da079ac56f80373a9a1be0bf8
• https://git.kernel.org/stable/c/0f6947f5f5208f6ebd4d76a82a4757e2839a23f8
• https://git.kernel.org/stable/c/1bbf82d9f961414d6c76a08f7f843ea068e0ab7b
• https://git.kernel.org/stable/c/33061d0fba51d2bf70a2ef9645f703c33fe8e438
• https://git.kernel.org/stable/c/92ee3c60ec9fe64404dc035e7c41277d74aa26cb
• https://git.kernel.org/stable/c/9cb6c40a6ebe4a0cfc9d6a181958211682cffea9
• https://git.kernel.org/stable/c/a42aa926843acca96c0dfbde2e835b8137f2f092
• https://git.kernel.org/stable/c/fbeb492694ce0441053de57699e1e2b7bc148a69