wifi: mt76: mt7921: Add PCIe AER handler support to prevent system crash

Summary

In the Linux kernel, the following vulnerability has been resolved: wifi: mt76: mt7921: Add PCIe AER handler support to prevent system crash When an AER error occurs and the bus is hung, the register reads return 0xFFFFFFFF, causing the DMA queue state to be corrupted and resulting in an invalid memory access when accessing q->desc[] or q->entry[]. Unable to handle kernel paging request at virtual address ffffffc01099eac0 pc : mt76_dma_add_buf+0x124/0x188 [mt76] lr : mt76_dma_rx_fill+0x11c/0x1d8 [mt76] sp : ffffffc016d9bbf0 x29: ffffffc016d9bc10 x28: 0000000000000000 x27: 0000000000000000 x26: ffffffb7855e50b8 x25: ffffffb80d04f000 x24: 0000000000000000 x23: 0000000000000ec0 x22: ffffffb796803648 x21: ffffffb796801f80 x20: ffffffb7968035f8 x19: 0000000000000ec0 x18: 0000000000000000 x17: 000000004ec00000 x16: 000000000ec00000 x15: ffffffc01099eac0 x14: 000000004ec00000 x13: 00000000ffc5a000 x12: ffffffc016d9bc32 x11: 00000000ffffffff x10: 0000000000000002 x9 : 0000000000000000 x8 : 000000000000b4ac x7 : 0000000000000a20 x6 : ffffffb6c1806400 x5 : 0000000000000000 x4 : ffffffb80d04f000 x3 : 0000000000000000 x2 : 0000000000000001 x1 : 000000000ec04000 x0 : ffffffb7968035f8 Call trace: mt76_dma_add_buf+0x124/0x188 [mt76 (HASH:1029 4)] mt76_dma_rx_reset+0xe8/0xfc [mt76 (HASH:1029 4)] mt7921_wpdma_reset+0x188/0x1b0 [mt7921e (HASH:ee48 5)] mt7921e_mac_reset+0x128/0x418 [mt7921e (HASH:ee48 5)] mt7921_mac_reset_work+0xac/0x1a8 [mt7921_common (HASH:f721 6)] process_one_work+0x188/0x514 worker_thread+0x12c/0x300 kthread+0x140/0x1fc ret_from_fork+0x10/0x30 Fix the invalid memory access by validating the DMA index read from the hardware before it is used as a queue index. An out-of-range value, such as the 0xFFFFFFFF returned while the bus is hung, is now clamped so it can no longer corrupt q->head or q->tail. In addition, check the bus_hung flag in mt7921_mac_reset_work() before attempting the reset sequence, reject MCU messages while the bus is hung, and install no-op bus operations when an unrecoverable AER error is detected, preventing further invalid hardware accesses. Due to hardware limitations - such as the lack of a connected hardware reset pin or the absence of host re-probe functionality - affected Wi-Fi devices may not fully recover to a normal operational state after certain errors, even with AER enabled.