In the Linux kernel, the following vulnerability has been resolved:
tcp: add accessors to read/set tp->snd_cwnd
We had various bugs over the years with code breaking the assumption that tp->snd_cwnd is greater than zero.
Lately, syzbot reported the WARNONONCE(!tp->priorcwnd) added in commit 8b8a321ff72c ("tcp: fix zero cwnd in tcpcwnd_reduction") can trigger, and without a repro we would have to spend considerable time finding the bug.
Instead of complaining too late, we want to catch where and when tp->snd_cwnd is set to an illegal value.