tee: amdtee: fix use-after-free vulnerability in amdtee_close_session

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: tee: amdtee: fix use-after-free vulnerability in amdtee_close_session There is a potential race condition in amdtee_close_session that may cause use-after-free in amdtee_open_session. For instance, if a session has refcount == 1, and one thread tries to free this session via: kref_put(&sess->refcount, destroy_session); the reference count will get decremented, and the next step would be to call destroy_session(). However, if in another thread, amdtee_open_session() is called before destroy_session() has completed execution, alloc_session() may return 'sess' that will be freed up later in destroy_session() leading to use-after-free in amdtee_open_session. To fix this issue, treat decrement of sess->refcount and removal of 'sess' from session list in destroy_session() as a critical section, so that it is executed atomically.

References

• https://git.kernel.org/stable/c/da7ce52a2f6c468946195b116615297d3d113a27
• https://git.kernel.org/stable/c/1680c82929bc14d706065f123dab77f2f1293116
• https://git.kernel.org/stable/c/60c3e7a00db954947c265b55099c21b216f2a05c
• https://git.kernel.org/stable/c/1c95574350cd63bc3c5c2fa06658010768f2a0ce
• https://git.kernel.org/stable/c/f4384b3e54ea813868bb81a861bf5b2406e15d8f