CVE-2023-53016

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

Bluetooth: Fix possible deadlock in rfcomm_sk_state_change

syzbot reports a possible deadlock in rfcomm_sk_state_change [1]. While rfcomm_sock_connect acquires the sk lock and waits for the rfcomm lock, rfcomm_sock_release could have the rfcomm lock and hit a deadlock for acquiring the sk lock. Heres a simplified flow:

rfcomm_sock_connect: lock_sock(sk) rfcomm_dlc_open: rfcomm_lock()

rfcomm_sock_release: rfcomm_sock_shutdown: rfcomm_lock() __rfcomm_dlc_close: rfcomm_k_state_change: lock_sock(sk)

This patch drops the sk lock before calling rfcomm_dlc_open to avoid the possible deadlock and holds sks reference count to prevent use-after-free after rfcomm_dlc_open completes.

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/17511bd84871f4a6106cb335616e086880313f3f
• https://git.kernel.org/stable/c/1d80d57ffcb55488f0ec0b77928d4f82d16b6a90
• https://git.kernel.org/stable/c/98aec50ff7f60cc6f2d6a4396b475c547e58b04d