CVE-2023-52749

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

spi: Fix null dereference on suspend

A race condition exists where a synchronous (noqueue) transfer can be active during a system suspend. This can cause a null pointer dereference exception to occur when the system resumes.

Example order of events leading to the exception:

1. spi_sync() calls __spi_transfer_message_noqueue() which sets ctlr->cur_msg
2. Spi transfer begins via spi_transfer_one_message()
3. System is suspended interrupting the transfer context
4. System is resumed
5. spi_controller_resume() calls spi_start_queue() which resets cur_msg to NULL
6. Spi transfer context resumes and spi_finalize_current_message() is called which dereferences cur_msg (which is now NULL)

Wait for synchronous transfers to complete before suspending by acquiring the bus mutex and setting/checking a suspend flag.

Weakness

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

Affected Software

Extended Description

A race condition occurs within concurrent environments, and it is effectively a property of a code sequence. Depending on the context, a code sequence may be in the form of a function call, a small number of instructions, a series of program invocations, etc. A race condition violates these properties, which are closely related:

A race condition exists when an “interfering code sequence” can still access the shared resource, violating exclusivity. The interfering code sequence could be “trusted” or “untrusted.” A trusted interfering code sequence occurs within the product; it cannot be modified by the attacker, and it can only be invoked indirectly. An untrusted interfering code sequence can be authored directly by the attacker, and typically it is external to the vulnerable product.

Potential Mitigations

• Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.
• Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/29.html

References

• https://git.kernel.org/stable/c/4ec4508db97502a12daee88c74782e8d35ced068
• https://git.kernel.org/stable/c/96474ea47dc67b0704392d59192b233c8197db0e
• https://git.kernel.org/stable/c/bef4a48f4ef798c4feddf045d49e53c8a97d5e37
• https://git.kernel.org/stable/c/4ec4508db97502a12daee88c74782e8d35ced068
• https://git.kernel.org/stable/c/96474ea47dc67b0704392d59192b233c8197db0e
• https://git.kernel.org/stable/c/bef4a48f4ef798c4feddf045d49e53c8a97d5e37