Vulnerability CVE-2024-26999
Published: 2024-05-01

Description:
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 you're using pmac_zilog as a serial console:

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

That's 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 it's not fatal, the serial port rx function ceases to work.
Also, the iteration limit doesn't 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"
didn't produce anything. So I don't think this code is needed any more.
Remove it.

 References:
https://git.kernel.org/stable/c/7a3bbe41efa55323b6ea3c35fa15941d4dbecdef
https://git.kernel.org/stable/c/bbaafbb4651fede8d3c3881601ecaa4f834f9d3f
https://git.kernel.org/stable/c/52aaf1ff14622a04148dbb9ccce6d9de5d534ea7
https://git.kernel.org/stable/c/ca09dfc3cfdf89e6af3ac24e1c6c0be5c575a729
https://git.kernel.org/stable/c/1be3226445362bfbf461c92a5bcdb1723f2e4907
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