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

Vulnerability Description

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 can't 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.

References

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