net: mvpp2: prevent buffer overflow in page_pool allocation

In the Linux kernel, the following vulnerability has been resolved: net: mvpp2: prevent buffer overflow in page_pool allocation The per‑processor buffering scheme is supported only if the number of pools (nrxqs * 2) does not exceed MVPP2_BM_MAX_POOLS (8). This is already checked in mvpp2_probe() during the initial activation of percpu_pools. However, mvpp2_change_mtu() may later call mvpp2_bm_switch_buffers(priv, true) without this check, which can lead to an out-of-bounds access in the priv->page_pool array in mvpp2_bm_init(). The array is sized to hold MVPP2_PORT_MAX_RXQ entries, and mvpp2_get_nrxqs() may return exactly that value. The per-CPU scheme then doubles it to nrxqs * 2, exceeding the array bounds. Check that the hardware version is MVPP22 or newer and that the number of pools (nrxqs * 2) does not exceed MVPP2_BM_MAX_POOLS before switching to per-CPU mode. Found by Linux Verification Center (linuxtesting.org) with SVACE.