CVE-2024-44951

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

serial: sc16is7xx: fix TX fifo corruption

Sometimes, when a packet is received on channel A at almost the same time as a packet is about to be transmitted on channel B, we observe with a logic analyzer that the received packet on channel A is transmitted on channel B. In other words, the Tx buffer data on channel B is corrupted with data from channel A.

The problem appeared since commit 4409df5866b7 (serial: sc16is7xx: change EFR lock to operate on each channels), which changed the EFR locking to operate on each channel instead of chip-wise.

This commit has introduced a regression, because the EFR lock is used not only to protect the EFR registers access, but also, in a very obscure and undocumented way, to protect access to the data buffer, which is shared by the Tx and Rx handlers, but also by each channel of the IC.

Fix this regression first by switching to kfifo_out_linear_ptr() in sc16is7xx_handle_tx() to eliminate the need for a shared Rx/Tx buffer.

Secondly, replace the chip-wise Rx buffer with a separate Rx buffer for each channel.

Weakness

The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors.

Affected Software

Extended Description

Locking is a type of synchronization behavior that ensures that multiple independently-operating processes or threads do not interfere with each other when accessing the same resource. All processes/threads are expected to follow the same steps for locking. If these steps are not followed precisely - or if no locking is done at all - then another process/thread could modify the shared resource in a way that is not visible or predictable to the original process. This can lead to data or memory corruption, denial of service, etc.

Potential Mitigations

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/25.html
• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/27.html

References

• https://git.kernel.org/stable/c/09cfe05e9907f3276887a20e267cc40e202f4fdd
• https://git.kernel.org/stable/c/133f4c00b8b2bfcacead9b81e7e8edfceb4b06c4