CVE-2022-48985 — net: mana: Fix race on per-CQ variable napi work_done

Affected: Linux

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

net: mana: Fix race on per-CQ variable napi work_done

After calling napi_complete_done(), the NAPIF_STATE_SCHED bit may be cleared, and another CPU can start napi thread and access per-CQ variable, cq->work_done. If the other thread (for example, from busy_poll) sets it to a value >= budget, this thread will continue to run when it should stop, and cause memory corruption and panic.

To fix this issue, save the per-CQ work_done variable in a local variable before napi_complete_done(), so it won't be corrupted by a possible concurrent thread after napi_complete_done().

Also, add a flag bit to advertise to the NIC firmware: the NAPI work_done variable race is fixed, so the driver is able to reliably support features like busy_poll.

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CVE-2022-48985 — net: mana: Fix race on per-CQ variable napi work_done