CVE-2024-26999

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

serial/pmac_zilog: Remove flawed mitigation for rx irq flood

The mitigation was intended to stop the irq completely. That may be better than a hard lock-up but it turns out that you get a crash anyway if youre using pmac_zilog as a serial console:

ttyPZ0: pmz: rx irq flood ! BUG: spinlock recursion on CPU#0, swapper/0

Thats because the pr_err() call in pmz_receive_chars() results in pmz_console_write() attempting to lock a spinlock already locked in pmz_interrupt(). With CONFIG_DEBUG_SPINLOCK=y, this produces a fatal BUG splat. The spinlock in question is the one in struct uart_port.

Even when its not fatal, the serial port rx function ceases to work. Also, the iteration limit doesnt play nicely with QEMU, as can be seen in the bug report linked below.

A web search for other reports of the error message pmz: rx irq flood didnt produce anything. So I dont think this code is needed any more. Remove it.

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/1be3226445362bfbf461c92a5bcdb1723f2e4907
• https://git.kernel.org/stable/c/52aaf1ff14622a04148dbb9ccce6d9de5d534ea7
• https://git.kernel.org/stable/c/69a02273e288011b521ee7c1f3ab2c23fda633ce
• https://git.kernel.org/stable/c/7a3bbe41efa55323b6ea3c35fa15941d4dbecdef
• https://git.kernel.org/stable/c/ab86cf6f8d24e63e9aca23da5108af1aa5483928
• https://git.kernel.org/stable/c/bbaafbb4651fede8d3c3881601ecaa4f834f9d3f
• https://git.kernel.org/stable/c/ca09dfc3cfdf89e6af3ac24e1c6c0be5c575a729
• https://git.kernel.org/stable/c/d679c816929d62af51c8e6d7fc0e165c9412d2f3
• https://git.kernel.org/stable/c/1be3226445362bfbf461c92a5bcdb1723f2e4907
• https://git.kernel.org/stable/c/52aaf1ff14622a04148dbb9ccce6d9de5d534ea7
• https://git.kernel.org/stable/c/69a02273e288011b521ee7c1f3ab2c23fda633ce
• https://git.kernel.org/stable/c/7a3bbe41efa55323b6ea3c35fa15941d4dbecdef
• https://git.kernel.org/stable/c/ab86cf6f8d24e63e9aca23da5108af1aa5483928
• https://git.kernel.org/stable/c/bbaafbb4651fede8d3c3881601ecaa4f834f9d3f
• https://git.kernel.org/stable/c/ca09dfc3cfdf89e6af3ac24e1c6c0be5c575a729
• https://git.kernel.org/stable/c/d679c816929d62af51c8e6d7fc0e165c9412d2f3
• https://lists.debian.org/debian-lts-announce/2024/06/msg00017.html
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/4EZ6PJW7VOZ224TD7N4JZNU6KV32ZJ53/
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/DAMSOZXJEPUOXW33WZYWCVAY7Z5S7OOY/
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/GCBZZEC7L7KTWWAS2NLJK6SO3IZIL4WW/