CVE-2026-74382

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

net/sched: cls_bpf: prevent unbounded recursion in offload rollback

Quan Sun reported [1] a stack overflow in clsbpfoffload_cmd().

Reproducer on netdevsim: add a skipsw clsbpf filter, set the bpftcaccept debugfs knob to 0, then tc filter replace. The replace calls tcsetupcbreplace() which fails. clsbpfoffloadcmd() then swaps prog/oldprog and recursively calls itself to roll back. But bpftcaccept=0 makes the rollback fail too, which triggers yet another rollback frame with the same arguments, and so on until the stack is exhausted.

bpftcaccept is just a convenient knob for the reproducer. Any driver whose tcsetupcb_replace() fails twice in a row can hit the same loop, so this is not a netdevsim-only issue.

Two ways to fix it:

1) Have the rollback call tcsetupcbadd() on oldprog instead of re-entering clsbpfoffloadcmd(). 2) Mark the rollback frame with a flag and skip a second-level rollback from inside it.

Go with (2). It is the smaller change and keeps the original behaviour: the rollback still goes through tcsetupcb_replace(), so the driver gets one real chance to restore its state. If that attempt also fails, we just return the original error instead of recursing.