CVE-2023-53624

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

net/sched: sch_fq: fix integer overflow of "credit"

if schfq is configured with "initial quantum" having values greater than INTMAX, the first assignment of "credit" does signed integer overflow to a very negative value. In this situation, the syzkaller script provided by Cristoph triggers the CPU soft-lockup warning even with few sockets. It's not an infinite loop, but "credit" wasn't probably meant to be minus 2Gb for each new flow. Capping "initial quantum" to INT_MAX proved to fix the issue.

v2: validation of "initial quantum" is done in fqpolicy, instead of open coding in fqchange() _ suggested by Jakub Kicinski